To update to the latest build, SSH to your instance and execute the following:
git pull origin master
sudo supervisorctl reload
Before executing the fourth command (sudo supervisorctl reload), which restarts your verifier, you may wish to consult the mesh page to see where your verifier is in the cycle. At the top of this page, the current cycle is displayed by descending age of last block verified. The verifiers at the top of the list have had the greatest time elapse since verifying a block, and the verifiers at the bottom of the list have had the least time elapse. The verifier in bold at the bottom of the list is the verifier of the current frozen edge.
If you watch this page for a short time, you'll quickly see how the verification cycle works. The page automatically refreshes every 5 seconds, which is slightly shorter than the block time of 7 seconds, so you should see all blocks as they are produced.
To ensure that your verifier is processing blocks when its next turn in the cycle arrives, you should restart it when it is near the bottom of the list. In the image below, the verifiers in the green-highlighted area are in the ideal range for restarting, and the verifiers in the red-highlighted area should not be restarted right now.
In short, if your verifier is toward the top of the list, it is going to verify a block soon. Wait for it to verify its block and move to the bottom of the list. Then, execute sudo supervisorctl reload to restart your verifier.