1. Make sure you follow directions.
Sometimes they want you to go to a page and pick a product you like sometimes you have to pick a favorite food or link back to them. If you don't do it write your name might not get counted.
2.Make sure they have a way to reach you. Just you because you have a gamil account don't mean they can contact you .You have to go one time in your profile and set your email on public. I have seen lots of blogs have to pick other winners because they did not have a way to get a hold of them. Or you can alway just leave your email address.
3. Search for your name on google often. Sometime you win and instead of emailing you they just post your name . I have found two wins like this that I would of missed, both book wins. I am so glad I didn't miss it. Check you google screen name
4.Good contest karma. Remember that.Most Bloggers that hold contest do so out of there on pocket and pay shipping. So only enter If you want the prize or know someone who could use it.
5. If you do win when you receive email them to tell them you received it and to say thanks. If they know the prize was appreciated they may have more giveaways.
6. A great way to find blog giveaways to win is to use google blog search. I search for, first giveaways, last giveaways, (people put last chance to enter and last day)theses key words bring up a lot of giveaways.
If they is anything i missed or you want to add just comment below and i will add it.