GreenDesic

Ants

Use vinegar to destroy ant trails. Without the trails, ants get confused and will hopefully stay outside.
Find the source where they are entering and dust the area with either cinnamon or black pepper.
Spray liquid soap diluted with water (roughly 1 or 2 tablespoons per quart of water) on your plants to keep ants out.
Spray peppermint around your home to keep ants from entering.

Wasps

Make a trap from an old soda bottle to catch wasps. C off the top 1/3 of the way down of a 2 liter bottle. Flip the top so that the bottle neck is facing down into the rest of the bottle. Tape or staple the bottle neck to the outside of the bottom piece so that it fits tight. Fill the bottle part way with sugar water. It also works well to line the top of the bottle with jam to help attract the wasps. Wasps will enter the bottle but will not be able to get out.
Wipe tea tree oil all over your wooden window frames, doors, and any wooden posts you might have.

Fruit Flies

Clean up any ripe fruit droppings and take out the trash, fruit flies lay their eggs in overripe fruit.
Fill a little bowl with apple cider vinegar so that the depth is approximately 1”. Cover with plastic wrap, take a tooth pick and punch a bunch of holes. Make sure the holes are big enough for them to get in, but small enough that they cannot get out. Do not put them around the edge. This trap will start working instantly. The flies will be attracted to the scent of the apple cider vinegar and enter though the little holes. Once inside, they will be trapped and not able to escape.

Slugs & Snails

Slugs like slate beer, so place bowls in areas of your garden where they are most active. The slugs will climb in to drink and will drown in the liquid.
Put up a bird feeder. Birds love snails and slugs, so the more birds you have around, the less slugs you should have to deal with.
Spread crushed eggshells where they are prone to travel; they won't travel over the rough surface.