Oh yeah, I love doing eye contacts.
Across the room, sometimes I wait for her to look first. When I know she's looking at me, I look at her. She will probably look away. If she looks at you again quickly, then look away, then look at you again, she's probably nervous. I did a smile at this point, and she responded pretty well.
And for conversations, I think eye contact is good for putting more tension. Let's say she says something that could be related to sex somehow (let's say she loves to swallow bananas), I'll say something like : Ohhh, I see... Then I'd hold eye contact for a while and maybe move my eyebrows, then do a slow and warm smile. She might start laughing and say sometimes like : What?! XD I think that doing a big grinny smile is too friendly.
Anyway, I think I'm getting too technical. Do whatever you feel is the best for you and just be natural.