You might say "customer service" is the key to success, but I prefer "code switching" because, although they are complementary skills, you can have great empathy and compassion yet still be incapable of communicating that to the customer in a way that works.

Don't get me wrong, I don't mean put on accents or use unnatural slang. Instead, listen. Match cadence as best you can in your own accent. Become familiar with various subcultures you might encounter so that you can be a better (active) listener. Learn and remember which regular customers can tolerate banter and to what extent. Develop thick skin (within reason).

Remember your regulars, but avoid assuming what they want.

Be consistent with your schedule.

Lots more but that's initial suggestions from one who has been on both sides of this.

You could become a bartender without ever having mixed a drink and hack it - much more important to understand people and how to keep the vibe lively.

Oh, and every bartender has lied on their resume at least once.

All managers really want is someone who is reliable, turns up on time and doesn't steal. Bars (especially night clubs) have a high staff turnover so people are always needed. When I needed a new job I would print out a CV on nice paper and walk round every bar in the city handing them in - that gives staff / management a first impression of you. Don't email or post. Be there and hand it over. Also, I found it much harder when applying for advertised jobs - more competition.

The work itself is not complex but is very physical. Be prepared to work unsocial hours and get called in because someone else has has phoned in sick (it happens a lot!). Be aware you're going to have to diffuse arguments and stop fights at some point. Tips tend to be garbage in the UK unless you're waiting tables. Be careful of your alcohol consumption -- the industry breeds alcoholics.