If you are new to playing the guitar or are picking it up after a long time, then you will be familiar with the pain in your fingertips. It's usually impossible to practice for longer than an hour at a go without feeling like you're stabbing your fingers. Thus you have to learn how to get past the pain so you can continue playing in the future. Here are some tips that will allow you extended practice hours and eventually a painless guitar playing experience.
Ow vs. OWWWWW!!
Learn to distinguish between slight discomfort and genuine pain. Guitar playing isn't about pushing yourself like there is no tomorrow. Regardless of whatever folklore you may have heard about Bryan Adams keeping it at it till his fingers bled, keep from over doing things yourself. If you notice grooves in the ends of your fingers from sliding and fretting the strings, and it gets painful to have a go at pressing against strings after half an hour of practice. This is quite normal, and the thing to do is to stop. Take a break and come back to it once the fingers are less sensitive. However, persistent pain (that doesn't go away) or unbearable discomfort that is immediate from when you pick up the instrument for practice is unusual, and you should probably seek medical advice before moving on.
Suck It Up
The most popular and widely-accepted strategy for dealing with sore fingers is to just face it for a while. If you manage to avoid both extremes of foolish bravery and unnecessary paranoia, what will typically happen is that your fingers will start forming callouses because of repeated friction against the strings. The soft, sensitive skin will, in time, develop to becoming rough and hard, and that is when they stop hurting. This stage, however, arrives only with considerable practice.
The problem with over-enthusiastic practice is that your skin may just give in to serious injury, and then practice becomes out of question for a good number weeks. You wouldn't want that! On the other hand, the callouses will not form unless you go through some initial discomfort, and you'll have to be both patient and persistent. It takes regular practice for up to a couple of months (usually a couple of weeks if you are at it daily) for the callouses to form.
Also remember that if you give up on practice for any elongated period of time, the skin regains its original texture and you are back to square one. Talk about motivation for continuous practice! Prepare to get your fingers soreness-free all over again if you are going to take a break.
While recommendations of adding super glue to your finger tips or the more realistic idea of using Band-Aids during the early days float around, you are really best advised to grit your teeth and go through it. Not only that it is worth it, it is also the only way to go if you intend to be a regular player. Any of the other tricks are at best temporary and at worst more harmful than helpful. That said, do seek professional medical help if your fingers show unusual symptoms of pain or injury. Under normal circumstances, once the initial period of forming callouses is out of the way, the fingers shouldn't hurt any more at all, and you should try to minimize the discomfort even in the early days by taking frequent breaks and, generally, not killing yourself. Put forth as much effort to learn this as you would to start a tattoo artist career, and you should be all set.