Advice here are appropriate for B2C segment (web-stores mostly). This presentaion about conversion rate is a part of serias on the topic.

1. 5 tips to
increase site
conversion
rate
For B2C
from
Dmitry Pushilin

2. Make an order simple
one step with mail an phone number is often enough.
Ask everything else you need personally.

3. Explain every step in
the order
if you ask mail - ensure you wouldn’t spam
if you ask a birthday say «We want to make a present for you»
if you can’t explain «why» - don’t ask it at all!

4. Use Symbols of Security

5. Show comments and
reviews
Motivate custumers share their opinion about goods and your
service.
Don’t hide negative comments: answer it and try to solve the
problem

6. Make social buttons and
widgets work
if you started several months ago and didn’t get any «likes» to
you facebook widget or to «the page» - don’t show it on the web-
site at all.

7. ...or just make the
lowest price ever and
free shipping to any
region
=)
Thanks for attention