The Hoodooist covers the necessary basics,

Type of Bar is self explanatory; is it a Hotel bar? Basement? Terrace, Al Fresco, Speakeasy, Cabaret?

Ideal for is similarly self explanatory; is it great for a date? Privacy? Small, or large groups? Time of day? Lounging, or dancing?

Damage is judged by your average London cocktail standards:
£ is normally anything under 8 pounds (almost mythical these days).
££ is your average round London, 8 to 11 GBP.
£££, from 11 upwards to 14.
££££, anything above. Common in hotel bars, these often get the harshest reviews – if you’re going to charge that much, you better wow.

And the rating system is stars out of 5:

Drinks: 3 stars is recommended, 4 stars is normally for the really good stuff, 5 stars are rare but worth it.
Their rating also reflects their prices; is it worth paying that much? If a mediocre 2 star drink charges 5 star prices, they’ll get a lower rating here.

Atmosphere: Covers decor, crowd, music and overall ambience. A place could look good, but handle music terribly, losing stars.

Service: Attentiveness, attitude. Are they willing to chat about their drinks with you? Or are they going to patronise you instead?