Best way to start a review site...

If possible, you might want to show them other sites that you run to let them know that you are a legitimate webmaster. Another thing that I do at times when requesting access for my review site is to let them know I'll also be pushing traffic directly to the review via other sites in my network so they have a direct traffic boost (as opposed to the SE traffic / bookmarker traffic, which you won't have yet since your site is new).
If you don't happen to have other sites that you can use for an example for the program, I'd say just go with asking. The worst that can happen is for that they say no, but I honestly can't say I've had many programs turn me down, even when I was first starting with my review site.

Great question and answer! Do you think adult web producers expect a positive review if they give temp membership access or will they accept a negative review as long as its fair?

In my experience I had no problems requesting access to pay sites for reviews, even when I initially started my site. If you have a review site already set up and have begun to review sites or at least list certain pay sites you shouldn't have any issues with obtaining user names and passwords.

In response to videosc's question it depends on how you approach the situation. Once a sponsor gives you access to their member area they usually don't ask for a link to the review or that you email them once you have finished. With that being said the choice is yours if you want to communicate with the sponsor about the result of your review.

Regardless if the sponsor knows the outcome of the review or not they shouldn't expect a positive review or treat you any differently as an affiliate if the review is negative or positive. A smart pay site owner will read reviews of their site(s) and take any negative comments in to account in order to improve upon their site(s).

Uh, make Excel Spreadsheets of Data.

A review is a review and doesn't have to be hysterically positive to get results anyway. To get your visitors to trust your opinion and advice, you need to be reasonably honest so you have to be able to write down negative stuff as well. Sponsors know that so we don't expect a positive review per se, we expect a fair review.

If you want to start off with our 14 sites feel free to hit me up for a user/pass.

Once you start to send any traffic to pay sites, they will contact you directly and provide any stuff you like.

we have 100 review sites in our list. As we shared access to all of them.

drom me a line for content/member cp acccess.
and ur review site URL too.

thanks.