I'm not going to get into the technicalities of listing your guitar or items of musical equipment here but thought I would go over some of the things I have learnt both as a customer and as a seller, all of which should help you get the best of deals for yourself. The packaging and delivery information relates to the UK, but I am sure a similar approach to that described may be useful elsewhere.

Timing For Buyers and Sellers
If you are selling don't set your auction to end during a weekday morning or afternoon since you will be missing out on many potential bidders who work normal hours and won't be available to make late bids end auctions after having pushed up the price, sometimes dramatically. By all means do some research on existing auctions selling items similar to those you wish to sell, but in the end you will probably find a weekday, or weekend, evening is the way to go. As to the actual ending time, well to check for the most active times try following eBay auctions which match ...

This is a common question so here is a very basic guide to choosing a size of guitar to suit your child:

4-6 years-of-age: either a 1/4-size guitar - or even a soprano or tenor size ukulele

6-8-years-of-age: a half-size guitar

8-12-years-of-age: a three-quarter-size guitar

12-years-of-age to adult: a full-size guitar

Of course children are not all the same so their height and the size of their hands and fingers will vary. The above details relate to the lower end of child size percentile. Always make the effort to visit a local music shop which stocks guitars of various sizes so your child can physically hold them and place fingers on their fingerboards. Some might disagree on this but I would recommend considering a small-for-age rather than large-for-age choice simply because any child struggling to reach the necessary frets to play even simple chords will usually lose interest in the instrument. 

As to the type of starter guitar to buy well, the general consensus tends to favour nylon ...