Alright guys, you want to be a gentleman, but you don't want crazy girls analyzing every word you emphasized and move you made in search of a hint that you like her. Right? I can relate. Not as a guy, of course, but a girl who has to listen to other girls interpret your words and actions. Anyway, so here's my advice to you guys, and my only suggestion is that whatever manly things you do for girls, make sure you don't single a girl out with your actions UNLESS you truly are trying to single her out. :)
1. If it's after dark, or late, walk a girl to her car, even if you're not leaving quite yet. Especially on campus or in big parking lots. Even if there are multiple girls walking out, offer to walk the whole group out. Girls will almost never ask you to walk them out, and they will most often say "not to worry about it" if you offer, so phrase it in such a way that girls don't feel bad. "Hey, can I walk you out?" or "Let me walk you out" will sound more like you want to do this for them then "Do you want me to walk you out?" which could be taken as "I will if you want me to, but I'm sure hoping you don't."
2. Unless you know a girl is anti-hugging, then hug her if you are hugging other girls. Don't hug some and high-five others within the same group (I don't know any girls who like high fives, by the way, just as a side note). And on that note, if a girl doesn't want to be hugged, respect that. Either you creep her out, or she has good reasons (such as past abuse).
3. If it's exceptionally late, or the weather is bad, or you know a girl is stopping for gas after dark, then ask her to text you when they get home. Sometimes it's nice to know someone besides our parents care if we get home okay.
So there you have it guys. Nothing major, not a long list, just a few simple ways you can let girls know you care for them like sisters. Just to reiterate, DO NOT SINGLE A GIRL OUT UNLESS YOU TRULY ARE INTERESTED IN PURSUING SOMETHING WITH HER. Otherwise, you will be the topic of tear-fest girls nights (if there was such thing) as your every action and words are compared to what you did for other girls. If you single a girl out that you don't like, well, that's just not very manly. ;-)
Fine print: Some girls may not feel the same way about this as I do, so don't feel discouraged if you get rejected a time or two.