Just make sure whatever you do on the side is truly on the side. Even if you code something up at work they may help some open source project you're interested

Just make sure whatever you do on the side is truly on the side. Even if you code something up at work they may help some open source project you're interested in, recode it away from the office on your own computer. In terms of your projects, stick to the "in no way competes with their business". This gets harder with larger companies, but after working there for any amount of time, you'll readily see which projects of yours will conflict with their business interests. If you're worried a project might conflict, propose it as an internal research initiative. You may luck out and get to work on something you really enjoy at work.