I'm not a fan of the 10% every week thing, but as someone who co-owned a web development firm, I can tell you we had a very simple contract with very clear terms about payment. If a big company wants to pay us on their own terms, then the agreement gets amended and everyone's happy. If they decide, after signing the contract, that they want to do things their own way, then sucks for them we wouldn't work on the project until we got payment.
So make sure your contracts say what you want them to say, and mention payment terms. If you're working with a larger company, chances are they'll mention the terms they use for payment. Either adapt your contract for that client, or find someone else to work with.
Be very careful in this situation, it's very easy for both sides to get confused which payment terms they are using. Make sure there is a single definitive contract for the project. Many companies you'll work with will assume they are using their standard terms, make sure it's clear that they are using your contract, and your terms.
So make sure your contracts say what you want them to say, and mention payment terms. If you're working with a larger company, chances are they'll mention the terms they use for payment. Either adapt your contract for that client, or find someone else to work with.
Once the rules are agreed on, late is late.