Agree with the other replies, but I get the engine as hot as I can first, the shit build up is usually soft and guey then and makes it a bit easier to get the injector out, as it cools it turns to concrete and then you can chip and scrape it way easier.

Also you might need a tool to remove the copper sealing washer from the head.

And be careful cleaning the injector, i just scrape the carbon off with a stanley knife, but DON'T clean the nozzle tip