First of all, women in their 20s are totally attainable in your 40s. So, if you want them go for it now. A lot of them, hot ones, don't really give a shit about age. I'd actually say it's more common for the hot ones not to care and to be looking more for personality than average looking girls. When guys can have anyone they want, they usually go for the most beautiful, and often youngest, girl. But when girls can have anyone, they go for the coolest guy, regardless of how he looks or how old he is.

You are as old as your companions. Make friends in the age group of women you want to date. Hang out with younger people when you go out. People generally don't care how old you are, but how old you act. If you hang out with younger people you start to mirror them naturally. Besides that it will give you the opportunity to meet more targets via friends of friends. Don't bring along your same-aged friends unless they are super cool. They can really drag you down socially.

Even if you don't like going out much anymore (who really does?), most girls in their 20s really like it, and you need be able to keep up if you want to hang with them. I find that as I get a bit older it becomes more important to be the life of the party and not the type to go home early. It's pretty easy to seem old and boring when it comes to partying. You don't have to drink as much as they do, but you need to be able to have just as much fun.

Your years must have made you cool and interesting. You need to be a step above your peers in a way. People will remember your age, it's different. It makes you stand out. It doesn't have to be a bad thing, but it's important to be conscious of the impression you are making. I see a lot of older people out in the bars/clubs... looking boring, and hanging with their older friends... looking old. I'm sure if I hung out with women my own age and went home early, I wouldn't get as many opportunities as I do with women in their 20s.

Dress age appropriately. This is more of a problem for women, so I won't go into it. But, just don't get into younger fashion. It will make you look older. Stick to sharp and classy. Don't be afraid to dress up a bit. Casual doesn't look young either. Guys seem to make that mistake a lot. If you're older, you can probably afford nicer clothes; wear them. Anyone in their 40s should always be well-dressed for the occasion.

One more little thing... it's ok to tease yourself about being old once in a while, let them tease you if they want. But, don't tease them about being young. Only perhaps rarely and in a very lighthearted manner. It comes across as condescending so easily. I dunno, I've just had bad luck with it.