In your opinion/experience, what makes an effective landing page?

I'm currently tweaking and experimenting with my landing pages but I'm curious to see what others think.

some points off the top of my head:

1. you identifying with the customer. "i was just like you"
2. giving them a time frame to act upon "after next week, we run out of copies"
3. presenting value to the customer, they should buy your product because... it's better than the competition due to X,Y,Z and because 20 other people say so, etc.

2. giving them a time frame to act upon "after next week, we run out of copies"

That's interesting. I have seen that done many times but I haven't yet tried that myself.

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big key is be up front if they have to pay shipping then say that in you ad and on the landing page to many people try to "trick" people into clicking for somethign free but that usually converts less.