Here are some things that helped me give up sugar during my last pregnancy:
Eat lots of protein--sugar cravings can mean you're low on protein
Cut out refined sugar and high fructose corn syrup (HFCS) completely first--eat maple syrup, honey, fruits and other more natural sugars when you want something sweet...they aren't as addictive. If you can kick the refined sugar, you'll probably find everything else easier to deal with in moderation.
Read labels: refined sugar and HFCS are in an insane amount of things--yogurt, bread, jam, peanut butter, everything processed basically. If you cut out the "hidden" refined sugars it will help you cut the craving. I find that the more sugar I eat, the more I want...so cutting out the hidden sugars helped me immensely (it's easier for me to buy bread/yogurt/etc that doesn't have sugar in it than to pass up a candy bar...and it still cuts down on your sugar intake the same way). You have to cut out "sugar," "cane juice," "cane syrup," "corn syrup," "high fructose corn syrup," etc... All the addictive "fake" stuff.
When you're craving something sweet--grab a piece of fruit (and something high in protein).
Good luck! Sugar is so tough--I'm pretty convinced it's just as addictive as some other drugs out there