First, a free trial is available on the main Windows Azure site--just click the "Free trial" option, which gives a 90-day trial.
The second option is if you have a MSDN subscription. As part of some MSDN subscriptions, you also get an amount of Windows Azure time, provided you live in a supported country. The versions that include Windows Azure are outlined at the Microsoft website. The amount of Windows Azure benefit depends on the version, which is detailed at this Windows Azure web page.
After you have the MSDN subscription activated, check the MSDN benefit at the Windows Azure/MSDN Benefits site. You will need a credit card to cover any resources you use beyond your included amount, but it won't be charged as long as you stay within your benefit limits. The MSDN benefit also has a great feature that implements a spending limit , disabling your subscription if your hit your included benefits to ensure your credit card doesn't end up with a huge bill!
You can check your current usage at the Windows Azure account page once you have signed up, but keep the following in mind:
- VMs count whether they're running or not, so create the VMs then remove them when you're done testing, to stop your time being used.
- Don't turn off the spending limit unless you want to be charged.
- Watch storage consumption.