Asking for too much information - Does the application ask personal information like your marital status, how many children you have, your age, ethnic background, etc? Employers have no business asking these questions. It is illegal for them to base your eligibility on these factors, and you are not required to give this information. Also do not give your credit card number, social security number or banking information to any company unless you know they are legitimate. The company will only need this information if they are actually hiring you. I recommend leaving that blank when applying for jobs. If you get hired, they should furnish you with a real tax form to fill out, where you will supply your social security number. (Don't just send it through email to them.) For banking information, they only need that if you are signing up for direct deposit, and they should give you an actual direct deposit form to fill out and fax or mail back. They should not need your credit card number for any reason. If they are paying you through Paypal or another online payment system, you can provide your Paypal email address to them, but do NOT give them the password! (Yes, I've actually seen a "company" requesting that of applicants before.)
Whois Search - Go to http://www.whois.com and search for the domain name (http://www.company.com). Who comes up as the Registrant? The company name, or an individual? It is possible that the website domain could be registered under the owner's personal name instead of the company name, so this alone doesn't mean they are a scam. Is it a private registration (you can't get the details)? Again, that alone doesn't mean it's a scam necessarily. Finally, look at the date the domain was registered. If the website gives details about how long the company has been in business and the domain registration differs greatly from that, be wary. If they claim they've been providing work at home jobs for 10 years, but upon looking up the domain name you see they've been online for a couple of months, that's a red flag.
Do some research - Write down the company name and the name the domain is registered under (if applicable). Go to http://www.google.com and type the company name in quotations, plus the word Scam, like this: "Company Name"+scam - see what comes up. Any negative experiences detailed on message forums? Do the same with the individual's name that the domain is registered under. (Also try replacing the word "scam" with the words, "scheme" or "fraud.") You can also search for pages that mention the company domain name, like this: "www.companywebsite.com" - Google will return results on any page that mentions that term. Then go to http://www.BBBOnline.com - http://www.RipoffReport.com - and http://www.ScamBusters.org and search for the company and individual's name.