If you’re using a regular small handsaw such as those you use for tree limbs and 4×4’s, it may prove a lot cheaper to buy a new one instead of getting it sharpened. If it’s a relatively modern saw used for random rough wood butchery, it’s seldom worth spending any money to sharpen it. It’d cost more than than the saw’s worth.
That said, doing it yourself with a few strokes on each tooth with the proper file and roughly the right angle, can do surprisingly well.
Shop around in your area if you can find a shop who sharpens blades for the cheap. If you can, then you can avoid buying for at least another while. I have a friend as well, an old time carpenter, who says the first thing to do with a new saw is to take it to be sharpened. The origional cutting edges are supposedly formed by the stamping process, and a sharpened tooth cuts much better.
That is, of course, assuming that it has an ordinary North American tooth pattern. Pruning saws are different. Japanese teeth are very difficult to sharpen. Saw sharpening is generally for heirloom or ultra-fine grade cabinet making saws. Ie: if you spend several hundred bucks on a Japanese Dozuki, damn straight you’re going to ship it to Japan to get it sharpened.