At workshops there are usually print critiques in which people show their work. There are some general themes which prevail and as I think that the same issues also apply when showing your work to a gallery, to a friend or a customer, it's worthwile commenting on those themes.
Deadly Sin # 1
Thou shalt not over sharpen. If I can see it, it's too much - unfortunately the photographer is often not aware of it - I can only suggest you check with someone with more experience if in doubt. Of course the problem really relates to sin # 2:
Deadly Sin # 2
Thou shalt not make prints bigger than the image file can justify. It would be nice if I could simply tell you how many pixels per inch but truth is that it depends on the subject matter and it's not enough to say landscape vs. sports or whatever - there are some landscape images which can make nice prints at 180 PPI and others that really do look better at 360 than at 300. Rocks tend to sharpen well, grass tends to oversharpen all too easily.
Deadly Sin # 3
Please, please, please don't make borderless large prints to show - they look terrible on tables and leaning against the wall, are hard to handle - they really don't show your work to best advantage - consider instead a large white border - see May 2006 blog and scroll down.
Deadly Sin # 4
Please don't show me images in plastic sleeves - and don't hold me up by slipping each print out of a plastic sleeve. Don't on the other hand treat the prints as holy relics only to be touched by white gloves. Some wear on the prints is the price to pay for showing them off.
Deadly Sin # 5
While it's true that prints don't always have to have a full range of tones from white to black, in general most good prints do and you'd better have a darn good reason if you don't. This is less of an issue in Photoshop since it's so darn easy to nail the white and black points but sure is a problem in the wet darkroom and isn't limited to beginners.
Deadly Sin # 6
Please don't use glossy paper - semi gloss is just fine, but something that looks like and probably is a sheet of plastic is less than appealing and the slightest mark spoils it. I cant think of a single reason to use high gloss paper.
Deadly Sin # 7
Take the time to flatten prints, and while you are at it, if they are flexible inkjet prints, think about mounting them, even temporarily. In most workshops prints are leaned against walls and sometimes passed around. A stiff backing makes this safer and easier and prints that gradually slide down the wall in a heap don't impress. Check with Light Impressions for some options for mounting work. Don't bother with overmats, they seem just to be a nuisence and won't lie flat when prints are leaned against the wall. These are your show and tell prints so if the material is less than archival - it's hardly the end of the world. That said, if showing them to a gallery, you probably should show that you know about archival.
Deadly Sin # 8
Yes, I know I promised only 7, but please take the time to put your prints in some sort of suitable container. Some people sneer at print boxes but frankly they are tidy, hold prints well and seem appropriate to the occasion. I've seen people slip prints out of albums, remove one print from a stack of 100, unzip economy size binders, brief cases, etc. I confess I haven't gone so far as buying a nice presntation box from Light Impressions, but I probably should. It's not that nice presentation makes up for weak photographs, it's that poor presentation detracts from good ones.
But you know what, the absolute worst sin of all is to not show your work around at all.