What you describe is absolutely the way to do it without looking weird. Don't be aggressive about it, accept a no or an awkward silence or similar as being a no, respond in a pleasant tone and not an aggressive one, and you should be pretty good to go without being seen as a creep, as long as you don't repeat it later. Of course, don't make a point of going around hitting on women in gyms or who are at work, but it can be done tactfully.