photo tricks
if you want the ultimate in quality, there are a few key things to pay attention to I think...
first, get your photos printed & scanned at a professional photo shop (like Hunts in Boston & Malden or send away to prodigitalphotos.com, which is the website i swear by), & not just at a local retail store (i.e. not Wal-Mart, Target, etc. etc.). This is significantly more expensive, but if quality is what you want, this is what you have to do. Also, it's a personal preference, but I think "matte" paper is much better for landscape pictures as opposed to "glossy" paper.
second, you MUST ask for a higher quality scan. A quick scan (with either a home scanner or a scanner used by a store/shop) will give you images that can't be enlarged without serious loss of quality. Ask for 150dpi or better (up to 300dpi) quality (I would never get my images scanned below 1 or 2 megabytes (1MB or 2MB) in size). For my favorite photographs, I often get a 30-50MB file scan (from slides), but I only use this if i'm trying to sell my photography at a show (as this can cost $2-$5 per picture to scan).
third, you need an awesome digital photo editor, like Adobe Photoshop (unfortunately, this one cost roughly $700 these days) or Adobe Imageready, which is a bit cheaper but doesn't have nearly as many cool features (still recommend it though...it's light years beyond standard photo editors). I use these programs for just about every single picture I take, as there are ALWAYS improvements (usually drastic ones) that can be made to photographs (cropping, color alteration, brush up on people, burning/dodging, etc.)
lastly, make sure that the file size is large when you are uploading to the internet. If you are using an online gallery sort of thing (like shutterfly or webshots), upload the files as jpeg quality, at least 1MB (but not more than 2MB) in size. A lot of people upload files that are 70kb and it shows. If you have your own website, make thumbnails that are 30-50kb in size and have those thumbnails link to pictures that are between 200kb-500kb in size. Photo editors will let you save pictures based on different levels of quality usually. Keep saving a file until you see it being saved as the size you want. You can also change the resolution to reduce the file size (ex. taking a 300dpi picture and changing it to 150dpi will change the file's overall size).
(and I used to consider myself a very capable computer geek!)
