Step 1: Install commit-msg hooks for gerrit
scp -p -P 29418 <gerrit_url>:hooks/commit-msg .git/hooks/
Step 2: Create normal commit and push (for Patchset1)
for example:
git add Server.java
git commit -m "server added"
git push origin HEAD:refs/for/master
Step 3: After doing some changes to Server.java
Finally to create new Patchset (Patchset 2)
git add Server.java
git commit --amend
git push origin HEAD:refs/for/master
Repeat step 3 for further Patches