The four courses (pairs of strings) of a Mandolin are tuned g,d'a'e''. The thickest pair (at the top for a right-handed player) are tuned to the note G above middle C. The next pair are tuned to the D above, the next to the A above that and the thinnest pair are tuned to the E above that. The strings are tuned in unison (both in the pair are tuned to the same note). The Mandolin can be tuned to an electronic tuner, another instrument (e.g. piano), or to itself. Often, tuning to concert pitch is desirable, but sometimes you may need to tune to another instrument which is not in concert pitch so that you can play ensemble. See Tuning a Mandolin for more details.
A Mandolin is normally rested in the lap and for a right-handed player, the fretboard and tuner point out to the left. Reverse this if you are a left-handed player. A Mandolin can also be used with a strap around the neck instead of rested in the lap in which case the Mandolin should be about the height needed for your strumming arm to be horizontal. The Mandolin should not be gripped. The strumming hand should be free to move the plectrum up and down on the strings without the hand or arm touching the soundboard, which will deaden the vibrations and quiten the sound. The hand which forms the notes on the fretboard should have the neck resting between the thumb and first finger (put your thumb pointing up to the ceiling and your first finger pointing straight out to the wall, now put the neck loosely just about where the nut is into the angle between the two). Curl your fingers over to the fretboard. Your first finger should be able to press down on each string at the first fret and your third finger should be able to press down on each string at the fifth fret. Your hand will naturally move from the vertical so your thumb now points slightly away from you. You may need to slide your hand slightly up the back of the neck to achieve this. Your strumming arm may just rest on the edge of the body and your plectrum should be in a position mid-way between the bridge and the end of the fretboard.
This refers to which hand you hold the plectrum in to pluck the strings above the soundboard. A right-handed player will therefore use the left hand to press down on the frets to form the notes and a left-handed player will use the right hand.
Frets are counted from the end of the neck where the tuners are. The frets are the horizontal pieces of metal set in the fingerboard against which the strings are 'stopped'. This shortens the string and raises the pitch. Many instruments have a plastic or ivory nut at the tuner end of the fingerboard, so the first fret back towards the bridge is fret 1. Some have a fret right next to the nut, and this is fret 0 so fret 1 is the next towards the bridge. If you can't get your finger between the fret and the nut, it's fret 0. Frets 5, 7 and 12 usually have an inlaid dot or design just before them. Fret 12 is often distinguished in some way, as stopping a string there sounds a note an octave above the open string. Sometimes, frets 3 and 9 or 10 are also marked in some way and others above fret 12 may be as well.
Choosing strings is tricky and there is no simple rule. Some of the factors which affect the string gauge are the age of the instrument, it's construction, the type of music you play and your preference for the sound. A light gauge will sound brighter but sustain less (and appear quieter) than a heavier gauge. Alloy strings (bronze or phosphor bronze) sound brighter than steel but need changing more frequently as the brightness dulls quite quickly with playing. Lighter strings tend to be single 'filaments' and heavier strings are 'wire wound' - a central core with a thin wire spirally wrapped around it. Nearly all mandolin strings are metal, although some baroque Neapolitan mandolins did use gut. These are now a specialist item.
A light set of metal strings are typically 09/09 12/12 18w/18w 26w/26w (the number e.g. 09 is the gauge, the pair is shown as 09/09 showing that both strings in the course are the same, and a 'w' shows that it's wire wound). A heavy set would typically be 12/12 16/16 26w/26w 40w/40w. Thes are only typical gauges - there are heavier and lighter sets and the individual gauges vary in different sets e.g. a heavy set from a different manufacturer may be 12/12 17/17 28w/28w 40w/40w. One of the important things is how much tension the set of tuned strings is putting on the mandolin - especially the neck. Modern mandolins have a truss rod in the neck - a metal rod which can be tensioned to keep the neck flat but older models did not and have a possibility of 'banana-ing' in a gentle curve making the srings at higher frets stand higher from the frets. Expert advice should also be sought about the gauge of strings a particular instrument an withstand the tension from.
The usual advice is that this is the same as the violin. First finger covers frets 1 and 2, second finger covers frets 3 and 4, the third finger covers frets 5 and 6 and the fourth finger is for fret 7. This is called 'first position'. Moving the first finger up to a fret normally played with the second finger (and playing with the other fingers up to 9th fret) is the second position and so on.
The major types of Mandolin are the Neapolitan bowl back ('tater bug') and the flat back.
The flat back comes in two types - A style or Artist and F style or Florentine.
Another type of flat back is guitar shaped and then there is the solid bodied electric mandolin.
You can find different electric mandolins for sale.
Buying cheap is false economy but don't go mad and find the most expensive one if you're a beginner. It's always best to try before you buy. Do you like the tone?, is the action easy to play?, is the neck straight?, are any frets buzzing? - there are many questions which you can only answer by looking and playing. However, having said that, a reputable dealer will supply by post a well set up instruments with all of the obvious defects removed. That just leaves 'Do I like the tone?' Distance selling regulations (in the UK at any rate) mean you can return an instrument within a reasonable time if you don't like it although you'll probably have to pay the postage if it's not being returned becauser of a defect. Mandolins are either hand made by Luthiers who take many weeks to make a beautiful instrument so they're expensive, or in a factory so they're cheaper. The cheapest factory made ones are plain, have cheap mechanicals (like tuners) and are usually not well finished. Finishing takes time (sanding, polishing, adjusting etc) so mid-range factory instruments have either been hand finished in the factory or by the dealer selling them. Expensive factory instruments should be very well finished as well as being 'fancier' and have better mechanical parts. Whatever you buy, it should be set up for playing. The better instruments use better types and quality of wood, metalwork and components which affect the tone, and have more time spent on them, making them presentable and playable. The very cheapest have plywood soundboards - avoid these they will never produce a good sound. Better instruments - even budget and modestly priced have a solid wood soundboard. You can tell by looking at the cross section in the sound hole - if it's plywood, you can see the layers.
It's an instrument tuning based on a standard note so that everyone plays in pitch. The standard is A - 440Hz or C - 523.3Hz. However, a tuning fork, well tuned piano or electronic tuner will give you concert pitch notes or tuning. If you're playing with a non-tunable instrument (like a concertina or melodeon that's not for some reason in concert pitch) you'll have to tune to it if you want to play together. If everyone tuned to concert, you'd be able to tune to an electronic tuner and join right in bang on pitch, but if that piano is a semitone south, everybody (who can) will have to tune down to it.
Personal preference really. There's plastic, nylon, tortoiseshell substitute (please don't use real tortoiseshell) even wood and metal. For the diehard recreationalists, there's probably quill. The thickness is whatever you feel comfortable playing with. Thinner usually means quieter but don't go mad. The very thick ones are for bass guitar. .40 mm is probably considered thin, .60mm - .70mm about medium and .80mm - 1mm is getting heavy.
Setting up is getting the mandolin playable. The bridge position, the action (the height of the strings above the fretboard - all the way along!), fret flatness (otherwise you'll get buzzes) and truss rod setting. Most of these should be left to a professional because there is a relationship between them and a consequence to tinkering with them. Especially leave the truss rod alone unless you know what you're doing. Basic advice is if it moves, you can set it yourself, if it doesn't move - leave it to a pro. A good dealer will always set up a mandolin before sale. They will set the action how you like it (high or low) and make sure it plays in tune all the way up the neck. A health check for your instrument once a year is a good idea.