Educate yourself on the bill or issue(s) prior to making contact with your legislators.
In your correspondence, state why you are concerned or encouraged about the issue or issues addressed by a particular bill. Try to put your thoughts in your own words. Your own personal experience and expertise can be most convincing.
Try to establish a relationship with the legislators in your district, and when contacting them, remember to tell them that they are your legislators. In general, you will have more influence as an actual constituent.
Try to communicate while the bill is in committee as well as when it is on the floor. Legislators are most receptive to input on bills that are on the calendar.
As always, treat your legislators with respect and kindness, even if you are upset about their position on a bill or other matter, or their response to you.