newbie,
If the shurbs aren't conifers, (bushes with needles and cones), go ahead and cut up to one third of the bush if you thik it will look good. No more. Unless it's really bad, like at the hose nozzle.
Anything with needles, sort of looks like a christmas tree, or a holly, wait til the weather cools off, like October.
Don't let anything grow into the neighbors back yard, lol, trim off any extremely low branches.
Just remember that after you are done, keep and eye out on the newly pruned shrubs. If you have no rain, and high temps, make sure to water them. Mulch wouldnt hurt either, and it would make them look and feel sooo much better.

post a pic... get an id..

AND THEN WE CAN ADVISE AS TO THE PROCEDURE...

there is really no way to give you any solid advice without knowing the plant...

ken

And you most certainly can't just cut back anything that isn't a conifer. Perhaps you can get someone from a local nursery to advise--but be advised that not all people from nurseries have any idea what they are talking about.

need to ID the plant first.