You can tell the types of pub apart because the brewery pubs will have the name of the brewery prominently displayed either on or near the sign, as in this example, which is round the corner from my house. Free houses say “Free House” somewhere on the pub, or sometimes on the sign itself, such as this one.
About 20 years ago in the town of Thame, Oxfordshire, where I went to school, there was a very old pub called the Saracen’s Head, that featured the decapitated head of a crusader-era Muslim. The pub shut down, and years later I moved to Connecticut. One day I took a drive to a British food store, to get Marmite and curry sauce and other stuff I was homesick for, and there on the wall of the store was the Saracen’s Head pub sign. I knew it was the right one because it displayed the name of the local brewery: A.B.C. (Aylesbury Brewing Company). Quite freaked me, I can tell you.
Interestingly, the setup in Ireland is quite different. Pubs are usually the name of the landlord (or original landlord), and have occasional supplementary names. Such as Neary’s in Dublin, which is on Chatham Street, and is also called the Chatham Lounge. In the Republic of Ireland they are all free houses, but most buy from the Guinness brewery which makes lots of other drinks under license, so there tends to be a near-uniform distribution of available beverages.
Pub signs in themselves are an ancient tradition, and while most follow a well-established formula, some can be quite witty. There was a racist joke on one near my parents, which was called, IIRC, ‘The Hopeless Task’, and the sign featured a washerwoman trying to get a black child “clean”. That was replaced in the 1980s…
Taking to outsiders depends really on the pub. In the worst-case scenario, in some pubs with well-established ‘regulars’, there can be a hostile silence when an outsider walks in (think American Werewolf in London). Sometimes there are curious looks before everyone carries on. In bigger places the visitor will be treated as anyone else. And in some places - and here Ireland is way better than the UK, or England at least - there is warmth and acceptance, and conversation flowing. Conversation is more common between strangers when sitting at the bar than sitting at a table.
Regarding etiquette - well the other day I was in the Bird & Baby (‘The Eagle and Child’ - where Tolkein and CS Lewis used to drink together) and was waiting at the bar to order. Suddenly I got a hard tap on the shoulder. “Excuse me, I was in the line,” said an angry Israeli tourist. I had to explain patiently that there is no line at a bar in a British pub. There’s a melee, but people tend to be served in order. He protested, but I held my ground, and when the barman caught my eye, I motioned that the Israeli guy was there first. This is how it’s done!
Some pubs are kid-friendly, but kids have to be off the premises before a certain hour - it used to be 7 pm but I think this has changed. In pubs with restaurants attached, kids are more likely to be allowed at any time. Also, some pubs have play areas, often outside in the ‘beer garden’.
Finally it is 99% likely there will be recorded music playing. The Harcourt Arms that I used to drink in didn’t have music, but it was very rare. In the UK, live music must be licensed, so it’s relatively rare, and when it happens a big deal is made out of it - amplifiers, a charge to get in, and so on. In Ireland, there is no such stipulation, and there’s more of a tradition of folk music, so live music is more common and incidental, and often occurs spontaneously - someone brings an instrument, someone else joins in, and “a session” happens.
ETA: Damn you, GorillaMan, for getting in there first! I shouldn’t have taken so long writing my post!