It's also a good idea to have a proof you have enough funds to support your stay.

The OP said they had dated. Is it now possible to do that without meeting in person? ;)

Purpose of your trip:
"I'm on holiday from school/work for five weeks and visiting a guy I like/dated/married and/or the SO's family."

The vast majority of times there isn't a whole lot more to it other than asking about where you are staying, when/how you are leaving and what you are doing on the trip. And maybe who paid for the trip.

My family has had foreign significant others travel alone and visit the US and their US significant others many such times; and other than one time it has never resulted in a delay of more than a couple of minutes for any of us. The one time it was a problem, it was because the person previously had a visa which allowed for some work in the US and immigration control (CBP or INS at the time) wanted to make sure the person wasn't there to work. [Being on summer/winter/spring break vacation from college/university, having one's own funds sufficient for ordinary living expenses and a return ticket probably helped things.]

True story: Once I flew into Canada from the US with my arm in a sling (I was hit by a car the week before). When I arrived at YHZ, I was sent to the "special section", extensively questioned about my injury, and asked if I had proof of sufficient funds during my stay over a holiday weekend. I responded by whipping out my Amex Platinum Card :D

But, just FYI, it is indeed considered fraud to enter the US on a tourist visa and do so (for which there can be consequences should the person subsequently apply for a green card).

We have not met in person. We've been long distance friends for two years, but then we fell and started long distance/online. This will be our first time meeting in person. I financed myself entirely for this trip, only because I do not like borrowing money or owing people.

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That's admirable. I hope it works out for you, OP. Enjoy the US! Are there any plans for him to come to Australia ?

That's going to raise some serious eyebrows...... I would stick with being a tourist also visiting a friend when not asked to elaborate.

Yes he is planning on coming down for my 21st birthday next year in August! I think the plan is to stay for 6 weeks!

Alright. I'll just answer all questions they ask me and when they ask my purpose for visiting, I will say I'm on a holiday and will be staying with a friend? I hope they don't ask me to elaborate.

But IF they do ask you to elaborate give a complete and truthful story the first time they ask, nothing worse than having to slowly pry the facts out of you.

Purpose of trips, funds, how long, proof of return plans - if that is clear there should be no problem.

No, it is not fraud to enter the US under the VWP (as the OP will be doing) and get married (which the OP says she will not be doing), as long as the tourist leaves the US within the 90 days.

It is also not fraud to enter the US with no intention to get married and every intention to leave, but then changing one's mind after a month. This is obviously not the easiest thing to prove, but if CBP granted admission under the VWP this means they believed the OP was not intending to immigrate, so they would need to prove the OP lied to them.

Where did you come up with that? Getting married in the US is commonly not fraud, and a tourist can get married in the US without it being so.

Coming to the U.S. by posing as a tourist with an intent to overstay and/or reside in the US by engaging in a sham marriage is fraud; but that is quite different than coming as a tourist and ending up getting married in the US while vacationing for a short while in the US.

That "first time meeting in person" may set off red flags. I've seen US women delayed or even ejected from the UK in circumstances like this; and the less likely you are able to show you have sufficient means to stay in a hotel/hostel for the duration of your stay, the more likely there are to be issues. And the UKBA tends to be much easier to deal with for visa-free tourists than the US CBP is for VWP countries' citizens.

Tourist visiting American family friends to get to know them and America would probably sell better, but then it may flop if there ends up being a lot more questions or even a call or physical meeting between CBP and your host/hosts while they determine what to do with you.

This sort of travel is certainly generally allowed, but will raise questions. Being honest that you are there to meet a friend whom you have been corresponding with online, but have never met is fine, provided you have a return ticket and funds to support yourself during that time period.

I would be somewhat conservative about the seriousness of the relationship. In reality, you have no idea what it will be like when you are together, so be open and honest with the border security that if it doesn't work out, you will leave (if they ask).

Agreed also that your friend and his immediate family should be prepared for a phone call from your first port of entry if there are any concerns raised by CBP.

As every indication is that you have honest intentions, honesty is the best policy. You are the least of CBP's concerns. If you don't, then they will likely see through it (as they should).

Enjoy the USA and best of luck to the two of you.

How did you find flyertalk if your not a frequent flyer?:D Customs / immigration usually take about a minute or 2 (at least in all the countries around the world that I have been). The officers are regular people just like you and I. You are doing nothing illegal or out of the ordinary for todays day and age. The worst that will happen is you will have to answer more then five questions. You should be more nervous about spending the holidays with you BFs family :D