What methods can I use to keep spiders out of my home and get rid of the ones that are already in it?

Spiders can be very beneficial. Remember that they go after bugs. But of course, they are unwelcome in most homes.

Here are a couple natural remedies that could help somewhat. Victors sells the glue traps and also a natural mint spray. I have personally used the glue traps with some success, especially near the garage doors and along walls and corners, etc. It is non-toxic. These glue traps really work great for me...they catch all kinds of critters. Spiders tend to go into the traps after the bugs. Change them out periodically, because they will fill up. [Moth balls are very toxic. Don't use them ever for anything.] Evidently the mint spray of Victors will "shoo" spiders away, but I haven't tried it. Mint is effective against quite a few critters.

Also, I tried something which seems to kill them as they enter the area, like the garage bay doors or patio. I bought a sack of cloves cheap at one of these discount foreign market groceries, got an old blender, added a bit of water and made a "clove smoothy". I strained and squeezed off the fluid through an old T-shirt, leaving just the muddy clove residue. I took the residue and 'plastered' it near the corners and floor of the garage bay doors, etc. I soon started noticing dead spiders. The fluid I use to spray to help drive bugs away from the back porch. Now, actually, I don't know for certain that the cloves paste killed the half dozen or so spiders I noticed around the area. Not having used any other substance (and certainly never chemical pesticides), my evaluation at this point is that the cloves paste did it.

A sidenote on cloves: Cloves tends to kill some internal parasites. Everybody has parasites which tend to "flourish" because of the accumulations of chemical and metal toxins in the body. People tend to underestimate the amount of toxic residues which they are absorb and accumulate in the body from the so very, very many products and the environment. Eventually ailments can develop in concert with parasites, and cancer can follow. I mention this because so many chemicals in so many products are considered "safe to use" in our society, yet they tend to predispose people and pets toward all kinds of "common" ailments and cancers. There are so very many natural alternatives and many lives could be happier as a result.

"Horse Apples" or hedge apples. This is the fruit of the Bois'd Arc tree, prominently found in the Midwest and south. The fruit is a big "green pimpled" apple about 4-6 inches in diameter. They start to fall to the ground about September. I have been conducting experiments with this fruit. Placing some of these around an area tends to repel spiders. The spiders just seem to vacate after awhile. Other pests are repelled also. Research on these horse apples is being done at an Iowa University currently.

Never ever use mothballs for any reason. They are extremely toxic.