You forgot one minor detail, odssstudents1.
Fist, he needs to go to each company's web page. Click on "Products offered", click on "common market contracts for your corporation", then offer at least some of your production to the local and/or common market.
In case you didn't know, shadrenrune (just covering the bases here), the local market is inside your country. A common market is between specific countries - and has to be set up or you can join one. You have to ask to join one.
Once you have product offered on your markets, you can go to each company's web page, and click on "Supplies", click on "common market contracts for your corporation", select "Local and Common Market" for everything, then click the "Modify Supply Contracts" button. This will create a contract to supply each company with everything that is available on your market.
A few things to note.
1. Companies usually produce more than 100% of their "expected production", but how much more varies. I limit my contracts to 100% of production IF the company was producing at only 100%. Thus, a company producing 117%, contracted at 100%, will put the excess 17% on the international market. I limit it to have some buffer against variability in production, supplies, hiring, efficiency, etc.. You don't have to; but I recommend something similar.
2. Once I finished creating all my contracts, I cancelled all the leftover offers I had. I'm not sure if it matters, though.
3. You will often run out of something before you've finished supplying all your companies. So, when you created a contract, and it only supplies 30% (or anything less than 100%) of that company's needs - you just contracted all of that product you offered on the market.
4. I just forgot what I was about to write.
4.1. The contract price will always be the current market price X the quality(Q). So if the world market price is rock bottom at the time, so will the price. That's good for the buying company, but sucks for your selling company. And vice versa if the price is pegged to the ceiling. The market price has to change by over 50% before your contracted price is updated.
4.2. Oh, now I remember - Clicking on 'Accept only local, or common market offers' - don't be fooled by the word "only". Your company will still go to the international market for whatever it can't find on the local & common markets. Whatever is not contracted will still be bought on the intl. market just like normal.
5. Make sure you have tons of high tech plebs before you buy more population. Your bought population will have the same makeup as your existing population. So if you're short high tech guys, then the population you buy will also be short high tech guys!
Whew, now my brain is emptied out.
If I'm wrong about anything, I'm sure someone with more experience will let you know. They've sure helped me a lot.
Best Regards.
The Evil Empire @ GR
P.S. Oh, and one last thing... (in Columbo's voice). You can make contracts with your country too. from the top menu, click on "trade", then "contracts", then "Common Market Contracts for your Country". You can create contracts, one at a time, or scroll all the way to the bottom and click on the bottom button "Accept Local and Common Market Contract Offers", then click "Confirm" To create them all at once. But as your population increases, so does their consumption. Which means what was contracted at 100% today won't be 100% a month from now.