During Undergrad or after?
If taken more than once will schools see all scores or the best/latest?
It depends on when you are planning to apply. If you are applying for fall (say fall 2017), you should aim to take it summer to fall of the year before (summer to fall 2016). This gives you time to retake if necessary before applications are due in the winter.
The GRE has “score select,” which lets you choose which scores you want to send where.