I'm a gallery represented photographer (at the Charles Baltivik Gallery in Provincetown), when starting out I got some great advice.
1) You can never ever lower your price. If you do this, the people who bought at the higher price will remember and not be happy. If a person bought one of your prints, they like your stuff and will probably buy more. I'd say half of my sales are from repeat collectors.
2) Chose a small number of sizes and crop all your work to those sizes. Believe it or not, inventory management of frames and mattes gets expensive and tedious. This means that sometimes your shot won't be cropped exactly the way you like it. Get over that. (And shoot wider than normal so you have some cropping freedom!)
3) Do not date your work where it is visible. Some collectors only buy fresh work, they'll ignore last years work.
4) When pricing, remember the gallery will get a cut, often around 50%. This needs to be taken into account when ensuring you don't sell at a loss. For example, you can get a good print for around $10, frame it yourself for about $40. Now, if you sell it for $80, gallery takes half. What's left for you? -$10.
5) Prints are cheap, frames are expensive, especially considering inventory. Make sure you can reuse your frames.
And frankly, just to make your life easier, just mark it NFS.