I use companies as clients. I have a different company set up for each product/initiative/MSA-contract, so for us it goes by product or initiative. I attach a form to each "Company" with information about that product/initiative/contract. When a project is opened, the user chooses the product/contract code. Since we are in the pharma/health industry; from that company entry I can prepopulate a lot of the information we need for the project. Example:
Company name is "Humira", from that I know the manufacturer is Abbvie, the therapeutic area is Arthritis/Crohn's/psoriasis, the billing cycle is 60 days, the buyer is Med Affairs, the contact is Jane Doe, the product is pharmaceutical, the product life cycle is post-launch, etc. All this is in calculated fields on the project form that pull from the company form.
This allows the user to not think about filling out a form and concentrate on getting the job done. Plus, it eliminates all the wrong choices you might see in a user-filled form.