How do you know these giveaways are legit?
After several years of entering I have a pretty good eye for what is a scam and what isn't! With that being said, I again only help promote these giveaways and if something makes you uneasy simply don't enter.
What if I don't get my prize?
That is something you'll have to take up with the blog owner/writer - typically they are great to work with and check in with the sponsor to get you your prize!
Will they notify me if I win?
It depends on the blog. I recommend subscribing to the blogs you enter so you can see if they post a winner - or you can bookmark and check back. In general they will email you though, so be sure to leave your email in your comment or somewhere they can find it to notify you!
Also, be sure to check your 'spam' folder and make sure no actual emails have wormed their way in there.
I'm not winning anything - why not?
I wish I had a magic ball - but it comes down to luck and persistence. The more you enter, the better your chances!