First of all, you need to realise that online dating to some extent is a numbers game. Not everyone you message is going to reply, that doesn't really matter though. If you contact enough women and only a fraction reply you will have more than enough to work with.

Your profile and your initial message really has to stand out. The numbers game works both ways. There are even more men on these sites than there are women, and they are all competing for attention. I made a fake female profile just to see what sort of thing men were sending and I was shocked to see just how many message women get in a day, and how lame a lot of those messages were.

Everyone has at least a couple of pictures were they are looking pretty good. If not, take some. Digital cameras mean that you can take a hundred just to pick out one or two where you are looking fairly good.
Don't post a picture of you holding a fish. Women don't care how big the fish you caught at the weekend was. Don't use a picture of you and your kids (if you have any), you may think it makes you look like a decent family orientated guy but it doesn't. Don't have pictures of anything other than yourself, it doesn't matter how great your car is, don't include it. Try and have at least one photo of you wearing a suit. Just put a suit on and take a picture. If you don't have the sort of job where you wear a suit every day you can say you took the picture before an interview, or before going to a wedding, something like that. Don't use any picture that makes you look loutish, or like a big drinker. No matter how great your body maybe for gods sake keep your shirt on. You will just look like a dick otherwise. You can always take advantage of this later. Don't have a picture where you are a distant dot in the background either. I find a decent portrait shot of your head down to midway of your torso is the best. Or just head and shoulders. Try and have at least three different pictures too. I read somewhere recently that women respond better if you are not looking directly into the camera, looking away slightly or looking at something else.

When it comes to the content of your profile there is really only one rule:

BE FUNNY

Ask any woman what she looks for in a man and sense of humour will always be somewhere in the top three. Don't waste time bigging yourself up or listing your hobbies and interests (nobody really cares!). Just make her laugh! Something I have found that works quite well is blatant lying. That being said I am honest about the fact that I am lying. The lies are so over the top that it is obvious. For example, I may say that I am a billionaire fireman (playing to the attraction stereotypes) that is being stalked by Megan Fox because I wont date her. Or that whilst I was on my way to collect a Nobel Prize for kissing that my private jet got diverted to Rwanda so I spent some time there building orphanages instead. You can really let your imagination run wild. Things like this also give women something to comment on when they reply to you and can make the conversation flow. It shows you are funny and do not take yourself too seriously, at the same time mocking the stereotypes. I don't claim that this is the best way, it is just something I have found quite effective. If you can think of other ways then try them out, experiment a little. I tend not to give too much away about myself in my profile because that leaves lots of lines of questioning open for the conversations that follow. At the end of my profile I usually include a couple of quirky facts about myself, which again are conversation starters. Don't boast with these, in fact I would go the other way and be a little self-deprecating. It is even better if it is something that other people can identify with. For example: "I don't know why, but I find triangle sandwiches just taste better than rectangular ones". It is kind of an amusing "me too" statement. again, a little imagination is required.

In general, try to be original. Don't use any of the clichéd one-liners or pick up lines that have been used a million times before. A good one-liner can be great but choose carefully and make sure it isn't one that is well known or obvious.

The first message is the hardest! A good looking woman will have hundreds so you have really got to stand out. back in the day of Love@Lycos the messages had a subject line too which was great, cos I would put in the subject line "OH MY GOD!!! I CAN'T BELIEVE THAT..." then the first line of the message would be "..... you fell for my dirty trick to read my message". Oh the mileage I had out of that one. But alas, POF does not have a subject line. First the DON'Ts -

Hi
Hi, How are you?
Hi, How was your weekend?

or any other dreary bullshit like that. When I set up that fake profile those 3 messages accounted for about 95% of all the messages. A first message that I have found works well on POF is this....

"Hi,
Managing to avoid all the weirdos and perverts on here so far?"

I also try to mention something from her profile (whilst still keeping it short)so it does not look like a copy and paste job, but not a compliment about her looks. I try and be a bit more original.

Again, I am interested in hearing others but I have found this quite effective. The reasons I think this works is because:
a) its different
b) it acknowledges a fact (i.e. uses a truism)
c) it subconsciously makes here catagorise you as NOT a weirdo or pervert
d) it is humorous
e) it elicits a response
f) it is a great conversation opener

From here you can start sharing horror stories of all "losers" on there whilst elevating both you and her above the pack.

So - wanna know the next step that REALLY seals the deal??