If it seems to good to be true -- it probably is.
If you have to pay a fee (or buy anything) to get started, it is probably a scam.
If you have to download software, give away personal info, or pay a fee before "learning a secret" to make money -- it is probably a scam.
Common Scams: Envelope stuffing, product assembly, mystery shopping, data entry, paid to surf.
There are legitimate data entry and work from home jobs -- but you find them the old fashion way; sending in a resume and applying for a job.