I don't think there is any quick way to check license infringing. But, there are way to avoid it.
first just don't google around and download stuff from where ever you hit. If you like any content, then look for license agreement around the download page. If you don't find any then look for contact information and ask them about it.(only if you know that the hosting site owner, is the owner of that asset)
secondly, never ever download from file sharing web site or torrents. Like rapidshare, megaupload, demonoid etc etc. They just host the file. There is no way to know who does it belong to or where did it came from.
it always ,a wise decision to ask a lawyer, but as you said, it not possible for every indie developers out there. But, sometimes if you get confused(very frequently) then you should go for it. Save you ass before its busted.
lastly, don't ever assume its ok to use it. License infringing can end up in jail time and/or fine(depending of the country you are in).
sometimes, some decent attitude can lead to indecent situation. Like if you name your game "X Edge", then Edge Game can sue you. Like they did to EA for the game Mirrors Edge. Edge game lost the case.But Edge games don't allow anyone to use the word Edge to any games.