I'm in my 50s and have been doing OD for about 4 months. I joined 4 sites - OK Cupid - found there to be an incredibly poor quality of men near my age and location so have deleted my profile.
Also joined Times Encounters but found men to be mostly entitled tossers. Got the impression that those in their 50s or even 60s were looking for women in their 40s - very disappointed with this site and won't renew my subscription.
Also not had much success with Match - had a couple of dates early on with men who I didn't fancy, but frankly there's not been much interest in me 
although I'm fuckin' gorgeous so won't renew my subscription.
My biggest success has been with POF, I think simply because there are so many men on it. I get a fairly constant stream of messages; I rarely initiate the messaging. I don't reply to anyone who I'm not remotely interested due to their photo being repulsive unflattering, or them posing with drunken mates or them messaging something like 'wannachat babe' or making misogynist comments in their profile.
I consider myself very choosy. I've had about 10 dates with nice men, but haven't been attracted to any of them, though most have wanted to see me again. I consider there are decent men on POF, but you have to hone your prat radar and not involve yourself in any way with the tossers. (Get over to the to the Dating thread - post or lurk, or do both as I do. You'll learn lots).
I've found a lot of men doing OD lie about their age and /or post old photos. If I'm considering meeting someone I now ask them to confirm how old they are and if their photo is recent. That way there's no surprises when we meet.
I like self help books so I'd say read a few - I like 'He's just not that into you'.
And I'd say (sorry going on a bit here), don't make OD the be all and end all of your existence - join other stuff like www.meetup.co sports clubs etc.
And don't take it all too seriously 
Best of luck.