Yesterday just turned on a publishing offer.
I find interesting writing down a list of things that should tell you if a publisher is good (serious) or not.
1) check their website. In my case their website was "under construction" and "we're just starting" isn't an excuse. Beside, if you're just starting how can I trust that you'll sell my games well?
2) check contracts spell errors. I got the contract sent to me three times and even in the "final" version there was a nice augusR instead of augusT just before the signature field (so how could they have missed it? also I think that if the date isn't valid, the contract could be claimed invalid!)
3) advance royalties... they say "we offer you 9000$ in advance" and you can be easily tricked (well they almost got me infact). then you read that you MAY get those AFTER 30 days OR release of the game in XXX country (was retail part of the deal). What if they don't manage to release it? I should work to adapt the games for multilanguage and don't expect any payment BEFORE starting? my games are ready, you can see them. I have concrete things to offer and they don't. So just ask for a IMMEDIATE payment of the half of those "advance royalties" otherwise you may never see them...
4) negotiate. Unless your game is very crap never accept the first offer they make. From first contract to last one, the money they offered was doubled so their first offer was really low if they can afford to offer double money...
5) LINKS request. That was almost fun: they required me to put a BANNER or a link from mine to their website and they wanted to sell my games with ESD at a LOWER price!! haha yes, the people come to me, then come there and see the same games at less price... wonder where they'd buy them? that would mean losing lot of sales! and that request also mean that they don't really know how to do marketing (never seen BFG or real asking for such a deal!!)
6) last but not least reputation. Ask around before signing with someone, even if experience varies, if all people say "yes had no problem with them" you SHOULD be safe

This is my list if someone want to put more advice/suggestions...