I love travelling ... and with 55 countries visited (most of em twice) and a total of 3 years on the road, most of it solo, I consider myself I know a thing or two about travelling.
Yeah, most important JUST GO, second follow your heart, but third make sure you have a true idea about a place before you head there.
Things to consider are what type are you, city vs nature, mountains vs beach, culture vs party etc. Or find the ideal mix place. Cost is also a major factor here and price levels of destinations vary considerably, eg a lovely day in Cambodia/Laos can cost you 10$ a day in Caribean 200$ for pretty much the same thing.
Read travel blog (like travelpod), watch the pictures on these blogs to get an idea about ambience and see forums like lonely planet thorn tree where you can get excellent advice ...