Deer develop trails that they will use for generations in search of food. Your garden is probably on their route if you see them frequently. Encourage them to take a different path by setting out a salt lick some distance from the garden. The deer may make a new path to get to the salt lick and thus bypass the garden.
Deer are particularly fond of some plants and not so fond of others. If you have deer-attracting plants in your garden or yard, you might want to replace them with deer-repelling plants to make your smorgasbord less tasty. Deer are particularly attracted to arbovitae, tulips, dogwoods, daylilies, hostas, hydrangeas and impatiens. They are especially partial to roses.
Among the common plants deer may reject, or at least not go to a lot of trouble to get to, are astibles, coneflowers, blackberry lilies, blue fescue, boxwood, butterfly bushes, blanket flowers, holly, irises, forget-me-nots and bleeding hearts. Figure out which of these plants would complement your garden and plant them around the perimeter. You can make these selections fit in with your landscaping plan by using them creatively. You could create a garden with a boxwood hedge or place small shrubs, such as holly or butterfly bush, as accents right in the garden itself. If you have a flower garden, include in it mints, daffodils, honey suckles, lilacs, forget-me-nots, snowdrops, autumn crocuses, lemon balms, lilies of the valley, larkspurs, spider flowers and straw flowers.
An 8-foot-high fence should be reasonably effective in keeping deer out of your garden, but you may have to go as high as 10 or 12 feet if there are a lot of deer in your area. Another solution would be to build two fences each about 4 feet high that are separated by about 5 feet. If all other fencing options fail, you may need to install an electric fence. Netting may also help keep the deer away from the edibles.