How to build a simple fish pond in your garden

1. Find something that holds water

You can use a horse trough, a wine barrel, an old sink or bath tub, a classy plastic drop in, black plastic in a hole, cement or anything else you can think of. Some things to keep in mind: if you are putting in fish, make sure the container doesn't poison them.  Fish can't tolerate much copper, so no copper fish ponds. They do seem to tolerate galvanized (zinc) coatings well. Make sure it is deep enough to not evaporate to quickly or heat up to much or freeze solid (a little ice on top is Ok). Also, if Raccoons are in the area it needs to be deep and have something to limit them, like chicken wire or heavy wire right below the surface, so fish can go trough but furry criminals cannot. Make sure the fish fits the container, no Koi in sinks! If your container has straight sides either keep it filled up all the time or make sure there is an escape route for anything that falls in you don't want a pond of death. Drowned pack rats aren't pretty.
After building a bunch of these, I REALLY like the horse trough. They last for years, they're fairly cheap, they are the right height to put a bench next to.  They're big and cheap. You can get a 500 gallon tank for about $200, a 200 gallon tank for about $100. Through a $50-100 solar pump into it, a couple of water plants, and a few gold fish from the pet store(10 for $5) and you've created a 'pond'

2.If you have fish make sure your pond is aerated with a pump or a Juncus plant.  Rushes act as  air pumps and will keep the water clear. Use big ones like Juncus textilis, Basket Rush for big ponds, mediumd rushes like Juncus effusus, Common Rush for medium ponds, and small ones like Juncus occidentalis, Western Rush for small ponds. 
A recirculating pump is another way to aerate a pond. They sell solar pumps for this purpose(look at the ads.) Electric ponds are rather expensive and noisy. Small deeper ponds work better than large shallow ponds.

3. Pick some plants to go in your pond

TaDa