1.  Direct your target audiences to the next step in the conversion funnel. 

• It must instantly communicate purpose of page, grab attention, and encourage viewers to stay.

2.  Keep Designs Simple.

• Do not use standard webpage navigation  (this primarily means your typical nav. bars at the top and bottom of a page), it might distract visitors from the main goal.
• Do include elements of your homepage (except the standard navigation of course), like texts, graphics, and imagery so visitors know that they are in the right place.
• Use images that portray the biggest benefit your product or service offers and/or use images that relate specifically to what you offer.
• State the strongest benefit that your product offers in your main headline. As the first thing a visitor sees, your headline serves as the biggest opportunity for improvements in conversion rate.
• Make the main copy brief and easy to read; use bulleted lists (for easier readability) to highlight your benefits from strongest to weakest.
• Put your call-to-action above the fold, focus on your primary objective, and  make links as clear as possible.

3.  Optimize your page to make it SEO/PPC friendly.

• Relate your page directly to search terms; match specific keywords – this not only includes copy but also images and call-to-action phrases that match those of PPC ads.

4.  Test multiple pages.

• Create multiple landing pages to target different customer segments.
• Keep them live for enough time to gather measurable results.

5.  Measure results by using various tools to gauge traffic.

• Google Analytics is a great way to track several metrics such as goals, conversions, time on page, bounce rate, etc.
  That's all, short and sweet - a brief summary of my recommended best practices. If you have anything to add, designers and marketers alike, feel free to comment below!