The most important advice I can give on this subject is to never leave the keys inside. Always keep them in your pocket, and if possible leave a window open. It's also a good idea to have a manual non-electric cable release for one of your doors, just in case of any accidental lockouts happen. Lets face it, however careful you are about it; eventually you will get side tracked, and leave the keys inside. So it's best that you plan ahead and get a cable release. This way even if your battery dies, you can still get in. Just be careful to keep the location of the release hidden to prevent break-ins.