Here is a basic reference for collaborative git commands:

Checkout a remote branch

# list branches first
git branch -a
# * master
# remotes/origin/branch_name
git checkout -b local_name remotes/origin/branch_name

Merging

# switch to master
git checkout master
# merge with experimental branch
git merge experimental

Create a tag

# list tags
git tag
# add a tag
git tag tagname
# push to remote
git push origin master --tags