I've made homemade pasta a couple of times in my young life. It's always laborious and time-consuming, but it's also tons-o-fun, especially if you can wrangle a friend or significant other (hint hint, DK) into doing it with you. Plus, there's nothing more satisfying than making something from scratch. It's like magic, the way the pasta just comes together.
That being said, making pasta from scratch is certainly not an exact science. You just have to do it a few times to figure out what's right for you - and it all depends on the temperature, humidity, type of flour, size of eggs, etc. Even though the perfect dough can't be scripted, here's a good place to start:
Egg pasta (pasta all'uovo)
3 cups flour (all-purpose or OO)
4 eggs (large)
1 tablespoon olive oil
Mound most of the flour in the center of a large wooden cutting board, reserving a portion for later. It's easy to add the reserved flour later to make "wet" dough drier, but it's very tough to add liquid to a dough that's too dry. 
Make a well in the middle of the flour and add the eggs and the olive oil. Using a fork, beat together the eggs and oil, and begin to incorporate the flour while still retaining the shape of the well - it should still look like a volcano. As you expand the well, keep pushing the flour up from the base of the mound to retain the well shape. The dough will start to come together once half of the flour has been incorporated. At this point you can start kneading 
the dough by hand, using the your palms. There will be stray knobby bits of egg and flour that you should just brush to the side of your board. Keep kneading the dough for 5 minutes. It should have the texture of soft play dough. Wrap it in plastic and let it rest in the fridge for half an hour.
Once the dough has rested, unwrap it and cut it into four portions - you will roll one portion at a time, and the rest of the dough should sit wrapped in the fridge until you're ready for it. Lightly flour the dough you're working with and send it through the pasta machine on the thickest setting. Fold it in half or into thirds and send it through again. 
You will have to roll the pasta on the same setting a number of times. I usually move on to the next setting when the pasta is smooth and unblemished - no cracks or tears in the dough. If your dough does start to rip, don't worry. You've moved to a thinner setting too quickly. Just drop the machine down to a thicker setting and re-roll the sheet. Be sure to dust it with a little flour every now and again. The pasta should never stick to your fingers, but should still be elastic.
As you continue rolling, the pasta will get loooooooong - a partner is a big help when you're trying to send these long sheets through the roller. But remember, you want to be able to comfortably eat the noodle, so you can cut a long sheet of pasta as needed.
Once you've rolled the sheet to your desired thickness, it's time to cut! You can do this by hand by folding the sheet over on itself and cutting lengthwise with a sharp knife. This is a great way to make pappardelle. Standard pasta machines include a cutting roller, usually for fettuccine and cappellini noodles. 
Once you've cut your noodles, drop them into salted boiling water for 90 seconds or until they float. There is no al dente for fresh pasta, but overcooking it will make it gummy and gross. Like I said, it's not an easy process, and it usually takes a good bit of time, but it's so wonderful to produce a beautiful meal out of a handful of flour and a couple of eggs. Trust me, it's worth it.
