Most of the folders will have a demo.sh script to run through the contract example. It's assumed you have goal installed natively.
Stepping through TEAL opcode-by-opcode is one of the best ways to understand how it works. To do this we use the tealdbg tool which comes with go-algorand. Use the following instructions as a quick guide on how to use it.
goal app create --creator $ADDR \
--approval-prog v4_loop/approval.teal \
--clear-prog v4_loop/clearstate.teal \
--global-byteslices 0 --global-ints 0 \
--local-byteslices 0 --local-ints 0 \
--dryrun-dump -o debug.dr
tealdbg debug v4_loop/approval.teal -d debug.dr --remote-debugging-port 9393