Spider Prevention: one cup vinegar, one cup pepper, a teaspoon of oil (like vegetable, olive, etc) and a teaspoon of dish soap. Pour into a spray bottle and spray along the outside frames of your door and windows. Remember to always refresh when it rains.
Spray windowsills and entryways with a solution of cup white vinegar, 1 cups water, and 20 drops of peppermint essential oil. (Eucalyptus oil purportedly works, too, but I find peppermint a more pleasant scent.