If you take time to put on mascara then you should take time to curl your eyelashes. I find that it makes such a difference, especially if you are not happy with your lash length, volume, or eye shape. Curling your lashes helps lift your eyes, and helps give the illusion of more lashes because it makes the lashes not normally noticed more visible.
When to curl lashes: After you have done your shadow and eye liner, but before you apply mascara.
How to curl: Use the eyelash curler by clamping down on your lashes once...don't pump the eyelash curler, there is no need. By clamping once and holding it down a few seconds you will see results, if you want a more dramatic curl clamp down one more time and hold. Repeat this for the other side.
What eyelash curler to use: Shu Uemura Eyelash Curler
This is a $19 product, but it is well worth it. Every makeup artist I know says it is their favorite, and anyone I've met who owns it or has just bought one LOVES it. When I use it on myself with enough mascara I've had people ask me if my lashes are fake. I have wasted time and money on eyelash curlers that didn't do much, so once I found this product I was hooked. The shape of the curler allows you to get close to your eye, the silicone pad in it and the design apply enough pressure so that a curl is created that will hold. Shu Uemura is known for their eyelash curler, and while they have a number of quality products this is what people return to them for the most. You can find it at Sephora, Ulta, Nordstrom or on Amazon.