Reduce
You could ask not to have a plastic straw in your drinks at a café or restaurant. If you use straws a lot you could have your own reusable alternative e.g. ones made out of hard plastic or metal.
Reuse
Plastic straws can be reused in a number of creative ways. This webpage has some great ideas.
Recycle
For advice on hard metal straws, see "Metal".
For advice on hard plastics straws, see "Plastics (hard)".