2. Filtration or purification pumps
If you go to a camping and outdoors supply store, you'll undoubtedly find many different kinds of pumps with filters and purifiers to make sure non-potable water goes in, but drinkable water comes out - right into your water bottle. This is done through a process of squeezing water through ceramic or charcoal filter and treating it with chemicals.
Some hi-tech water bottles have this process built into them, so that you don't need to pump water into a separate one; the purification process happens as you squeeze or suck water directly into your mouth.
3. Purification drops and tablets
A simple and inexpensive - but not necessarily the best tasting - method of purifying wild water is by dropping in a couple of purification tablets or drops. The most common chemical used is iodine, but chlorine or potassium permanganate are also effective. Let the chemicals treat the water for at least 20 minutes before consuming, and mix it with powdered mixes to mask any of its taste.
4. Make an evaporation trap in the ground.
All of the previous methods require you to carry water or have a water source nearby - but what if you don't have any? According to NatureSkills.com, you can pull moisture out of the earth by digging a hole in the ground and inserting a container on the bottom. Cover the hole with plastic so that no moisture escapes, and put a small weight (a rock perhaps) in the center of the cover so that there's a dip in the center. When the water evaporates from the ground upwards, it condenses on the cover and drips down into the container.
Of course this last method isn't the fastest way to get potable water, so just try and remember to bring some. However, in the event of an emergency, remember this technique - along with a container and some sort of plastic cover.