Landing pages are great for different reasons:
1) reviews/comparisons for different products. Here is a
very bad example I created:
http://www.connexins.com/BackPain
You will see I have reviewed several products about the same topic. All of the links are my Clickbank affiliate links.
2) pre-sell a specific product OR relate a specific product to a specific target or market. I have also successfully used landing pages to promote only one product.
3) Using a landing page as an opt-in form (aka squeeze page):
You provide information that hit certain buttons of your target market, and then entice them with a giveaway or something of that sort to have them enter their names and email addresses... then, by email, you can establish a relationship with your opt-in list by providing them with useful information, reviews, and once you develop trust, you can start promoting certain products.
There are probably other purposes for landing pages, but I am kind of spacing out right now... anyway, here are important elements of a good landing page:
1) an attention-grabbing title that hits a button or creates doubt/concern in your target population.
2) in your text, use key phrases or concerns of your target market. For example, notice in my landing page example above, I said "are you worried that you're destined for a life of pain", or "do you long to the simple things in life...", etc. Now, I decided to use these phrases because in my online research, I have found that these are some of the common concerns of people who are experiencing chronic back pain.
3) reviews of different products giving them "grades" or "ranks".
4) clear exit links to your affiliate products
5) Visuals! Show pictures that represent the mental/physical state of your target population. Toward the top of the page, it's good to show a picture of the problem (a picture of someone hunched over b/c of the back pain) and at the end a picture of someone who is happy to give his partner a piggy back ride (obviously someone who does not suffer from back pain)... sorry, it's lame, but I think the principle works well.
Also, keep in mind that the purpose of a landing page is to convert! So, no distractions, I don't even put Google Ads (because my goal is not earn 30 or 40 cents per click, I want to convert my affiliate links and earn 14 or 15 dollars).
Now, how do you promote a landing page? Tons of ways:
1) PPC
2) Write a blog entry! Now, sticking with the back pain example, you could write a blog entry (assuming that you have a blog about back pain) about the importance of exercises to eliminate back pain. Then you put a link to the landing page with affiliate links to products about specific, useful, or helpful exercises.
3) An Ezine Article! In the author bio box, you can say something like, "To Discover Proven Exercises To Help You Eliminate Back Pain, Visit My Back Pain Exercises Reviews" or something like that.
4) Squidoo Lens! Create a Squidoo lens or two with useful information that pertain to people who suffer from back pain, then link to your landing page.
5) From your own website. If you have a website about back pain, it would be a good idea to link to your landing page following an article
6) Any Other Way You Think Of!
This by no means is a comprehensive review/guide to landing pages, this was just a rambling session that captures my experiences with landing pages. I hope this was a little helpful
Sherif