Other methods include: tax (build housing, people will give you $$s/ turn)
mine ore, and sell it (explore planets first)
food (prob most $$ but a little hard for a newbie :) ) (build agri. infra. You make food per turn, which you sell on the market)
for miners: you make/sell minerals, or build industry to make CG`s (and sell on market, you need to buy raw materials to make CG`s)