I've sold stacks of ukes and some personal thoughts to share:
1. at a minimum take 20% off the RRP (sometimes more) as a baseline asking price, even if your uke is near new. That way everyone feels like they're getting a good deal.
2. take lots of good, detailed pics and offer as detailed description of specs as you are able.
3. no, most shops will not do trade ins or take commissions. Except shops that explicitly deal with trading, buying and selling second hand stuff. However in such instances you will probably only get around 1/3 of the market value rice, making it a total waste of time unles you are really desperate for immediate cash.
4. an ad in the local paper?
5. contact local uke groups with a flyer re your for sale instrument
6. try and provide a video sound and visual sample in your ad. This often has a really strong impact.
7. reconsider your decision not to ship. Your market will open up exponentially. Shipping isn't as difficult or complicated as you may think provided you pack with due care.
all the best with your sales!