Experience is always the best way to learn. Don't worry, we all remortgage are homes to buy shit names to begin with
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As pointed out, forums are a good starting point... as well as this one which there's a few others which mainly focus on gTLDs (Global domains). Not sure I can mention the names here... so feel free to PM me.
Dnjournal.com is a great news site. domainnamewire.com is also pretty good.
If you're a total newbie you could also try namenewbie.com (content seems to be a little dated on this site, but most of what is on there is still solid advice). Site is owned by Ron, the same guy who runs dnjournal.com.
Hope this helps and good luck!
- Rob