You can hang wood fascia boards to prevent water damage to your roof, but they also have some cosmetic benefits. You need to spend time both preparing and hanging wood boards to help get a tight fit and minimize the need for replacements and repairs.
Measure and cut your wood fascia boards so that they are as close to the required dimensions as possible. It's acceptable to overshoot your measurements by a little bit, since the fascia can be sanded down after you hang it, but try not to cut it too short.
Prepare to hang your wood fascia boards by priming and painting them. Pay special attention to the ends of each piece, since that is where moisture is most likely to enter. Give fascia boards several days to dry before you get ready to install them.
Find out where the beams are located along your exterior walls. Mark these locations with a slight scratch so that you can use them to support your wood fascia boards.
Ask another person to help you support the wood fascia while you hang it. This person should be able to bear most of the weight on his own, since you may need to use both hands to nail down the fascia. The ideal position to prop up the board will be close to the center, but for longer boards, you may need a third person (and a third ladder).
Hammer in nails at both the top and bottom of the wood fascia. You can place the bottom nail so that it comes up through the base of the fascia and into the soffit to make it less visible. The top nail shouldn't be angled, since it will be less likely to hit a supporting beam.
Check up on your fascia every year while you clean your gutters. Wood is prone to rotting, since moisture can become trapped between the fascia and the house. Poke at the wood joints and consider replacing or repairing some of the pieces if they feel soft or start to crumble.
Examine your soffit boards at the first sign of any decay in the fascia. Be especially careful about hanging fascia during wet days, since the extra exposed wood will be at a high risk for moisture damage while you are working.
If you decide to switch to a vinyl fascia, then you can repair any rotted wood and use it as a base for attaching the vinyl.