How do I get set up on Signet?
You have two options to get set up on a Signet. One is to set up your own independent custom Signet that you can control. The other option is to use the default Signet set up and administered by Kalle Alm and AJ Towns. I will focus on the latter here.
Currently as of the time of writing (August 2020) the Signet PR has been merged into Bitcoin Core, but is not in a release yet, which means you need to compile Bitcoin Core's master branch yourself.
Once you have successfully built the master branch you should be able to use the
-signet flag e.g.
./src/bitcoind -daemon -signet
./src/bitcoin-cli -signet getnewaddress
To obtain some Signet Bitcoin there is a Signet faucet here: https://signetfaucet.com/
You can track Signet transactions with the Signet block explorer here: https://explorer.bc-2.jp/
For more details see Kalle's workshop at Advancing Bitcoin 2020 that shows you how to make Taproot transactions on Signet and debug Taproot scripts using Kalle's Bitcoin script debugger btcdeb. (Beware that the workshop is from before Signet was merged into Bitcoin Core, so some of the details are outdated.)