Paid to promote is an additional method of earning, most commonly attached to PTR sites. The first thing you need to know are what the terms and phrases you will see in the PTP section actually mean, so I'll go through them now.
Approved Sites This is a list of sites where you are permitted to advertise your PTP page at, this will vary from site to site
CPM This means cost per thousand, M is a Roman Numeral that means 1000. So when you see PTP advertised at $0.60 CPM, this means for every 1000 credits you earn are worth $0.60.
Credit Each person that views your PTP page will earn you a predetermined number of credits, the number of credits awarded are dependant on what tier the member who viewed your ad is.

Invalid Hit This is a hit to your page that will not earn you credit. It can be because the member didn't let the page load properly before closing the page down, it can be a repeat visit - meaning they have already clicked on your page within the last 24 hours, perhaps at another site your page is also advertised at, or, a hit from a site that is not listed in the approved sites directory.
Targeting This is where you can target an advert for your PTP page to a specific audience, with PTP you may try to target your ad to members of Tier 1 and 2 countries as they will earn you more credits per view.
Tiers There are four tiers (some sites will have five tiers), each tier consists of a group of countries. The higher the tier, the more credits you earn, so a member in the UK, which is a Tier 1 country, will earn more credits for you when they visit your page, than a member in China, which is a Tier 4 country.
Unique Hit This is a view to your PTP page from a member that has not visited the page in the last 12/24 hours which ever is applicable (most are 24, but a few sites offer 12 hour unique visits).
Valid Hit This is a hit that has been credited to your account, because the member that viewed the ad allowed the page to load and had not visited it in the past 12/24 hours (whichever is applicable)
Some programs with PTP's credit cash to your account automatically for each valid hit you receive to your PTP link whereas in most programs, the credits will get accumulated until you redeem them yourself.
Some sites will offer additional banners to use within this section and some sites list all the banners in your members referral centre section. The main thing to remember when using PTP is that use the correct URL at the correct time. To help me I list the PTP link on the same document that has the rest of my ref banners and URL's but I bold the PTP and display it in a different colour. By doing that way, it is easier for me to select the appropriate link that I need.
Each site will offer different PTP rates, one site may state a $0.60 CPM, whilst another offers $0.80. Each view of your PTP will earn a specified number of credits. How many credits depends on where the viewer is located. A user in the UK will earn more credits per view for you as they are in a Tier 1 country, whilst a member in China will earn you less credits for the same view as they are in a Tier 4 country. All the information about how that program defines their Tiers is listed under "Tiers Info", this is broadly the same for most sites but its always best to double check first. For this reason most members will try and target their views to Tier 1 and 2 countries, therefore earning them more credits per view. Each site will convert the credits to cash at a different rate, so you need to check that before you start your campaign as well.
You must always check the conditions of use for the PTP feature at each individual site, some programs require you to click a certain number of links, whilst others may have no conditions.
Once you know where to advertise and how much your credits are worth and how many credits will be earned for the different Tiers, you are ready to go. You can either buy advertising for you PTP ads, you can use click exchanges (you will click another members PTP link and in return they will click yours), you can list them in your signature at forums, or you can use traffic exchanges. Most people will use a combination of all these, but what you must ensure is that you are only using approved sites for displaying you link. If you use a site that is not on this list, every view received will be invalid. You can see what percentage of invalid hits (along with all the other information you need) by clicking "Statistics", always check back here regularly, try and keep your "Invalid" statistics as low as possible because some owners may suspend your PTP page if this percentage gets to big. Again this can vary from site to site.