The easiest way is to use a waterproof mascara (this one by L'Oreal is great), although wearing waterproof every day isn't always ideal. Aside from this, there's actually several other things you can do.
1. Be careful with your eye cream. Thick eye creams are moist and often contain oils that can break down your mascara and cause smudging, so either use a smaller amount, or skip the eye cream in the AM and only use it at night. There are also great eye gels you could use in the morning (like this one from Boscia) that shouldn't produce the smudging effect.
2. Powder your eye area. A lot of women are hesitant to powder around their eyes because a dry appearance enhances fine lines, but if you're using a minimal amount of powder, you won't have this problem. After you've applied your concealer and before you apply mascara, use a small brush and a bit of loose translucent powder. Make sure you dust it all the way under your lower lash line, and also all over your eyelid since this are naturally produces oils.
3. Don't use mascara on your lower lashes. If this is the area where you constantly get smudging, skip mascara here. You could always try getting a lash tint to darken and enhance the lashes, or even use waterproof mascara on your lower lashes only if this is your problem area.