The House narrowly passed the AHCA by a few votes; the final vote was 217-213, with 20 Republicans and all Democrats opposing the bill. Something for everyone to do ASAP is call and write your senators, even if you have a Democratic senator.
You can find out how to contact you Senators here: https://www.senate.gov/senators/contact/
Here's an optional sample script for calling:
My name is (FIRST AND LAST NAME) a constituent from (CITY AND STATE)
I am calling to urge the Senator to vote no on the AHCA. The AHCA will cause millions to lose their healthcare and premiums will skyrocket for the poor, the elderly, and those with pre-existing conditions. Health care should not be a partisan issue and I am asking that Senator (SENATOR’S NAME) vote NO on the AHCA.
After you call, follow up with an email or letter using the same text.