I'm with Luis on this one, don't rush it.
For magazines your best bet is to contact them regarding their usage terms, usually they pay 20$-20£ for normal usage. The ones I contacted asked me to either send them slides, or previews on a cd and they'd ask for high res scans when they decided what to use. In my opinion, if you haven't got alot of intersting stuff, it's not worth spending hour after hour scanning, if in the end they only decide to use one or two shots..
For other commercial usages, it's quite difficult, since most of them have their own photographers, and the ones who don't try to beg photos for free of sites like this one.
Regarding quality, if the publisher only wants to use a small image, even stuff scanned on a flatbed will be good enough.