Always give a very honest description and have some good pictures as well. Describe any damage honestly. Give mileage, service history, reg year etc. dont let anyone ride it unless they have paid for it in full with cash or a cleared cheque, dont fall for any of the scams invloving extra payments and promises of free collection for a mysterious overseas buyer etc. Bid to buy, not to look etc! Be ready for people to mess you about.
As the others have said you're just using ebay as another marketing tool but reaching a wider audience, so be prepared for even more idiots contacting you!
Be as honest as possible with everything - think of it from the buyer's perspective as you'd only be disappointed to travel some distance to view a "minter" only to find it's more like a "munter"!!
A good tip is to try and negotiate a sale outside of ebay through the use of the "this is for sale elsewhere, so I can withdraw it" wording, and then pull the auction to save the large fees they charge.
Ebay isn't expensive to advertise and their gallery auctions are very good. Get as many pics as you can prepared and put the best 4-6 up, and offer to email the rest to anyone who is interested. You may want to put a contact (mobile) number on for people to call direct - at least that way you can turn it off at night!
Steer clear of anything other than a cash deal if poss' there have been articles in MCN about fake building society cheques and bankers drafts, check with your bank exactly how long it takes to clear and ask them what there policy is on clearing, the main scam on e-bay has been buyers offering to pay by western union, don't go there, it is not a guarantee of payment, my next door neighbour was nearly caught when he sold his tank on e-bay, yes I said tank.