When I brew coffee I always brew by weight instead of by volume. This is a more accurate and consistent way to measure your water-to-coffee ratio, which I like to keep between 16 - 20:1 (usually 17:1 for my taste).
Weigh your coffee before you grind it for better accuracy and weigh it again after you've added it to the pot to make sure you're not leaving any grounds behind in the grinder.
With the Chemex, you should start by pouring about 100g of water first and let the coffee "bloom." This is where the coffee lets off a lot of CO2 and makes shiny, oil-covered bubbles. As the bloom is settling I use a chopstick to stir the coffee around to make sure it all gets wet and there are no dry pockets of coffee.
I then add the rest of the water in two or three more pours, pouring in a circular motion so that the turbulence from the pour agitates the grounds in the filter to prevent water channels from forming through the coffee mound.
I also like to keep the fire under the kettle between pours so that the water stays at a good temp — about 210°, just shy of the boiling point. This will keep your coffee mound in your filter at the optimal brewing temp of between 195° and 202°.