Concrete screeds are used for the purpose of leveling out concrete that is wet. Unless you want concrete that is lumpy, using one is highly recommended. Here are some tips for when you choose to use a screed:

Get a tool
Often times people want to use wood instead of a real screed that is designed for this specific purpose. The surfaces that need to be smoothed out are frequently wider than ten feet. That would require a long board that could be very heavy. Also, there is a good chance the board could be slightly warped. Both of those reasons could leave you a surface that you’re not happy with because it can dip into the concrete. An actual screed tool is made of aluminum and will not warp.

The process
Adjust your screed to where there is enough room on both sides for you and your helper to grab. Start at one end of the freshly poured concrete and work your way towards the other end in an inch-by-inch sawing motion. The sawing motion can be avoided of you have a power screed vibrator attached to the middle, which will save you a lot of time and effort. A third person should be equipped with a concrete-filled shovel putting extra into spots that are low areas. Go back over these areas after you have reached the end.