Do not mix up 'over' and 'under' in connection with promising and delivering.
Over-promise and under-delivery is not the right combination. Either deliver as promised or - less preferred - over-deliver or under-promise.

Do provide guidance on items that can be managed and you feel certain about.
Don't give guidance because people demand you, as a company you have to live with the consequence.

Do avoid overly positive spin.

Do have an easy-to-navigate website, which is complete and up-to-date.
It should provide (potential) investors with a wealth of information on the company, such as reports, fact sheets, press releases, webcasts, etc.

Don't try and place a valuation on your shares as a company: that is the market's job.
Financial factors that prompt investment interest are cash flow, return on invested capital; strong and sustainable financial performance.