Of course, you always want to keep your silhouette from coming down on the water above the fish. This will send them running for cover instantly. Remember, their biggest dangers usually come from above, so your shadow moving across the water will put all of them down very fast. It's also a benefit to have the sun at your back so you can better see the water, your line, etc. If this means that you'll have to come at the stream from a different angle, so be it. Better that you spend some extra time getting into the water from a more difficult spot, than scaring the fish so badly there won't be any fishing at all.
Some anglers like to use polarized sun glasses. These will allow you to see into the water & let you see the fish. Obviously, that can be a great benefit. However, I personally decided years ago not to use them. This is because I had the same problem a lot of other anglers have when using polarized glasses: I strike too soon & miss the trout!! Of course with practice & discipline you can learn to slow your strike down, but I never did. If you decide to use polarized sunglasses for the first time, be ready for this & force yourself to delay setting the hook - if your nerves can handle it.
The sun also changes the way the trout see the fly. If you're dry fly fishing & seem to be killing them while the sun is on the water, but get nothing when the sun goes behind the clouds, try changing to a different dry fly. Make sure that the fly you change to has a different profile, like say going from a Catskill style to a paradun style. This just might do the trick & will tell you that - in this particular situation - the profile of your dry fly is more important than the color.
The sun can add difficulties to our approaches & plans , but with a little thought & adjustments we can actually use it to our benefit.