I sent out some responces to Craigslist postings. Most have resulted in scam e-mails telling me to go to a website that they linked to so you can get your credit scores or take an IQ test. Aside from the e-mail links showing a diffrent site when you hover the mouse over them, the e-mail addresses they were sent from will not accept responces.
First, if they send you a link hover your mouse over it. Is it sending you to a different site? Is it one of the shorted links? Then it is more then likley a scam.
Most companies will only require a credit check when they are looking to hire you, if at all. They will never do one before they do an interview. They might have you fill out a PDF of an application to bring in with you at most.
Most notably beyondjobs.com is the biggest scam I have seen. I tried them, then my spam folder started filling up. Since then I always avoid them. Because there are jumping through hoops and then there is handing over every bit of information about you. If you do sign up with them you will find an insane increse in spam mail. they also work under diffrent guises. Engenerjobs.com being another of their sites.
The only thing you can really do Is look for postings that give you a good deal of information to work with. If you get an e-mail asking you to follow a link, take a test and then give them your score they are probably not real. Send them a polite e-mail explaining that you don't feel comfortable with their request. If you get anything other then a return notice then you are very lucky.
If you suspect a job posting might be a scam then don't waste your time applying for it. If they are promising a great deal of money for an entry level position then don't waste your time with it. They can be found on any job site that allows public posting and never seem to give up.