I make good eye contact when I'm pissed off at someone and want to intimidate them (at 150 lbs I need all the help I can get
), when I'm expected to (interviews, etc), or when it's someone I like and I want to show that I care about what they're saying. Otherwise I don't really bother to look straight at them for the entire conversation.
If making direct eye contact with someone is really troublesome, try their nose or forehead instead. It'll look close enough and might be easier.