internet scams how to avoid??

this is just crazy I'm getting 2 to 3 messages a day from scammers off of craiglsist, they have it all --swith there answers but not a one can call but there shipped can pick up-- I've probably ruined a few legit msgs because so many sound the same?

What can happen with giving out my email address? what are they wanting it for -- this seems more important now that the item for sale?

Anyone know what the scam is in my email? thanks Lawrence