Poison - if you've only just started the enterprise, I recommend pumping it full of cash, getting the "build more corporations" booster to extend registration, and building three corporations a game month for a week or two. Aiming for a Game Level (e.g. the one where you need 180 corporations) is a good idea. This will take 10 days if you are using the booster and building 3 corps a month. Remember to queue more corporations twice a day.
Once you have around 180 or so corporations, stop building corps for a bit and let the ones you've just built upgrade. Once your profit is consistently in the black, continue building corporations at whatever speed you like.
The most important principles of enterprises are:
1) Diversify your holdings. Invest in different product types so that if one product type has a surplus you don't go down the toilet.
2) Fire and forget. Once you've built a corporation, you shouldn't really need to check it as long as your trade strategies are decent. I've checked each of my corps twice after I've built them - once to change the name, once to set up ASQ. If you're having a lot of trouble with profit, it may be worthwhile to check your corps to see if they are making money.
3) Only build in countries with low tax and decent- to high-welfare. Many a vet will tell you that welfare doesn't really matter, but it can affect your production.
That's about it. Try not to build in C3s; select around 30 countries (including your own) to build corps in and build in them until they run out of workers. Try to fill up countries with 6 corps (12 if they're your own) before selecting new countries. The very best countries have stable Presidents (generally those who are active on the forums and are in a fed or CM), plenty of workers, less than 20% tax, and more than 100 Welfare.
Good luck!