If you have some trees that you need to chop down, it’s not that hard to cut trees down yourself. To cut a tree down without a professional arborist:
Cut a wedge up to 1/3 of the width of the tree. The wedge should be out of the side of the tree in the direction you want the tree to fall in. Assuming that the tree isn’t rotten (because this will make it weaker, you might want significantly less than 1/3) and the weight of the tree is spread evenly or hanging in the direction you want the tree to fall (otherwise you might need to cut it branch by branch until the weight is away from the direction you want to cut!).
When you’re cutting the wedge, the saw should suggest the direction the tree will fall in (90 degrees from the blade angle). Don’t cut your wedge more than 1/3 of the side of the tree otherwise it’s dangerous. My personal preference is to cut using a manual saw (rather than chainsaw) and keep cutting until the weight of the tree makes it difficult to cut (it will grab the blade). At this point, you will know that the tree will start to fall if you cut any further. I then make my wedge this deep. Sometimes once I’ve cut my wedge, I then do a little cut to make the wedge a little deeper.
Note that I am note an arborist and that cutting trees down can be a very dangerous business. I take no responsibility for your actions following my advice and recommend contacting a professional arborist if the tree is large.
Now that you have your wedge in the direction you want the tree to fall, the weight of the tree’s branches seems to be central or over the area you want the tree to fall, you’re ready to make the cut that fells the tree. Make a cut in the opposite side to the wedge you have cut out, a good few inches above the wedge. You won’t need to cut more than 1/3 of the way before the tree will start to fall; when this happens, just stand back and make small cuts as required.
If you have help, before cutting, you might want to climb the tree and rig up some ropes with pulleys to have friends pull the tree in the direction you want it to fall in addition to the above.
Obviously, some trees can be more complex, such as if they are next to property, over power-lines, have multiple tree trunks, etc… In which case, I would hire an arborist who is insured 😉