...plants, flowers, evergreens etc? I just don't know how far to cut them down.

When it comes to pruning flowers I cut back a good amount of the plant to make them grow more flowers. With your your gvergreens , take a good look at them, how bad are they, it won't hurt them to be cut back in the spring.That way they have all summer to fill in and get fuller. As for most flowers just pick off the dead flowers after they die and your plant will love you for it . Then save the seed head for next year, that way you don't have to buy seeds all the time. I save all the seeds I can from my flowers and I how have a yard that is so full of flowers that grow all summer.

Get some help the first time, practical help from cooperative extension for example, they can advise you not only on pruning plants or flowers but also fertilizing, composting, landscaping, and they have master gardeners.