A contract makes sure both parties are aware of all terms, and creates a legally binding document that ensures you will be properly compensated for the work that you do. Make sure the work you're going to be doing is clearly outlined, as well as the payment. If your client wants to pay a set amount initially and the rest on completion, or stagger payments then this should be written up in the contract so everyone knows where they stand. All freelance businesses are different, so spend some time thinking about your personal terms and conditions and include these in the contracts that you send to clients. Don't forget to include potential costs for travel and any other expenses, and be clear on what the deliverables are with the end product as well as the time frame. Be clear of the consequences of non-payment, too, so that they can be aware of what will happen if they don’t pay. This could include seeking the services of a debt collection company, a blacklist of your services or whatever else you decide. 

Depending on how payment will be made and the time frame outlined in your contract, it can be worth setting up a payment schedule and/ or reminders for payment. If you send out a payment reminder before the due date, it gives your client chance to schedule the payment or send the information over to their billing department for a timely payment. If you have accounting software it will likely have these kinds of features that you can set up at the start of the job and automate. If not, you will need to manually schedule this, so be organised. 

Avoid sharing sensitive information with clients, even those that seem like legitimate businesses. While services like Paypal will involve fees, it's safe for both buyer and seller so is a good way to accept payments as a freelancer. Clients can pay in any currency and as long as your account is in good standing your payment will be received and ready to transfer into your bank account right away.