I'm assuming you are going to keep goldfish? Make sure you have some underwater plants like hornwort, anacharis, or basically anything else, bushy type plants are best. Some piles of rocks, or sunken driftwood helps too. These are important for the goldfish to lay eggs on and for the babies to hide in, cuz the parents and other adult fish will eat the babies. Nature will make sure your fish breed, at least mine always do, and I do nothing special. When you see lots of fish chasing each other around, and sometimes splashing, they are in spawning mode.
I've done this for 7 years now, babies every single year! some years more survive than other years, but some always make it, as long as they have places to hide.