Boy, is Meteorman right! I'd like to have $10 for every time I've helped with a new saw that "won't cut right," only to find that the new owner seems not to have noticed in the manual that there are guides BELOW the table!
And as to tension, I NEVER leave the blade under tension. To make sure, I release the tension each time I shut the saw off. Habit has me resetting the tension lever every time I go to the saw to turn it on. Especially important with those pricey carbide blades. Can't 'seem to get the guys at the shop to do the same.
BTW, if you are shopping for a bandsaw--new or used--look at the guides. Figure in what it's going to cost you when you realize that you really need to upgrade those puppies. A fellow furnituremaker runs a 36" bandsaw built in 1895. Bought it as "scrap." Babbit top bearing and bronze on the bottom. Wheels have steel spokes, but the rims are wood. Runs like a dream, but one of the things he did when he rehabbed it was to get the best guides he could find and fit 'em to the saw.