Under promise, over deliver!
When you accept a role there is a mutual agreement that you will learn your lines, show up on time, and give your best performance.
How can you outdo that?
What can you offer?
How can you bring more to the table than any other actor?
For a low budget film you can offer to take behind the scenes photos with a point and shoot camera. If you have a large social media following you can offer to promote the film to your fans and help it gain more exposure.
If you are great with computers you can offer to start a Facebook page for the film or start the paper work to get the film on IMDb.
With doing all of this extra work to go above and beyond, remember to not let it compromise your performance. You were hired to perform first and foremost, the extra work helps you make a lasting impression and makes people want to work with you time and time again.
Directors and casting directors want professionalism and high quality work above all.