Most Helpful Guy
Have your shit together, be interesting to talk to, and look presentable.
Particularly the first one. As guys get older, they don't want to put up with the drama that seems to be attached to a lot of younger women. By mid 30s your starting to see the bigger picture, starting to see the longer game, so all of that petty personal drama stuff seems... well.. petty. It's draining to deal with, and meaningless for the most part.
By the mid 30s a lot of guys are starting to realize that there is more to life than sex as well, so being able to actually hold down an interesting conversation becomes much more important. Sex, while fun, is not something you want to be doing 24/7, so there needs to be an interesting person that can keep his attention for those times you are together with clothes on.
In terms of appearance, it's not going to be about looking as hot as a super model. Mid 30s start getting guys a bit more practical. They will accept you as you are (if you are within their 'acceptable' range, anyway), but you will have to look presentable. It doesn't mean a ton of make-up or hours doing your hair, but just... looking nice. Not looking like you were partying all night, high on drugs, is appreciated. Not looking like you slept in the library in your clothes studying all night. Whatever. It's about working with what you have and not trying too hard to make it appear like you are over-compensating or trying to be something you are not.