I usually improve as to what the city needs, while keeping forests around as long as possible for the 'free' hammer. Chopping alot early can be really tiring for your workers and they won't get much else done. You shouldn't need cottages early before your 4th city I think, but be sure to pick out some spots for them to be placed later. make sure you get roads to rivers and coasts for the easy trade routes. Thats about it for vanilla that I can think up.