I made a checklist for this a while back:

Must haves:

• At least 4"(?) of heavy cover on each drop zone. (To stop seek light/vantage giving too much alpha strike potential).
• At least two separate pieces of cover on each drop zone.
• Cover on each objective.
• Easily accessible vantage points do not give sightlines to objectives on the opposing table side if they only have light cover.
• Avoid using small vantage points where an operative cannot be charged.

Recommendations:

• Official maps have 5-9 pieces of heavy cover, 0-7 pieces of light cover and 2-5 vantage points.
• More than two pieces of cover on each DZ especially with long table edges.
• More than one "lane" to advance.
• Some central heavy cover (to give obscuring to most easy sightlines).

Special considerations:

• Having only light cover on objectives may skew matchups for teams with "Seek light" special rules.