adapt your build orders to your civ advantages:
- briton: 5 vills on sheep instead of 6.. less lumberjacks when fast castling. In BF, mine stone instead of gold (sell stone to age up) and spam tc's
- celts/teuts: less lumberjacks needed
- mongols : abuse hunt bonus .. always.. and get deer 100%
always look at your map... and if you play on explored maps like BF, goddamn abuse it.. find boar spots, find small lakes, etc. I hate when people have a pond near their base with shore fish and don't get em.
hmm, what else, don't usually do wheelbarrow on feudal unless you're on full feudal fights (specially nomad).
generally for booming games like BF, where your eco is all.. avoid excess of certain resources. if much food, start making eco upgrades (the mining camp ones, the others are an obvious must earlier), if much wood make a mill surrounded by farms, if much gold make monks and get relics, if much stone save up for a castle or send some vills to build stuff as you never want to have too many vills on stone. All of this is obviously supposing you're between the 15-25 min marks. But excess of food is not common.