John Steed, that most debonair and English of the gentleman adventurers, is a difficult character to emulate. Educated at Eton and Oxford, and having served in the Second World War, he is the epitome of the suave but tough gentleman who could never have an ordinary job. Even Ralph Fiennes, who played him in the motion picture The Avengers, didn't come up to scratch. Roger Moore and Pierce Brosnan would have done about as well as Fiennes, and Sean Connery would have been laughable in the role. Patrick Macnee, who played him in the television series, really is an Old Etonian and, even better, was actually expelled for being something of a scoundrel. During the Second World War, he was an officer in the Royal Navy, which could only have added to the right kind of bearing for playing Steed.
Again, appearance is paramount. In a fair number of episodes, Macnee designed Steed's clothes himself, and they took on a rather 'mod' appearance. (Real gentlemen often fancy themselves as tailors, which may be one of the reasons why Savile Row tailors were elevated to the ranks of gentlemen.) Steed's normal attire always includes a bowler hat, which he doubtless acquired from James Lock of London, the original and still the premier supplier of bowlers. The colour of the bowler goes with whatever suit he happens to be wearing. In the earlier parts of the series, Steed often wore dark, grey check or chalk stripe suits, but when Macnee designed them, they were usually shades of brown or grey. The jackets always tended to be single-breasted and double vented. He often wore a waistcoat to match his suit. His shirts were usually white, cream or similar pale shades. A paisley tie cropped up several times in the series. When Mrs Peel and Tara King were his partners, he wore Chelsea boots, laceless elasticated footwear which were standard issue for mods.
Steed never uses a gun. His weapons are his steel-lined bowler, and his umbrella. The umbrella, often cane-handled, would have been from James Smith of London, the most famous suppliers of umbrellas and walking sticks for the gentry. The umbrella actually sheaths a sword, but I always felt that it didn't really suit Steed.
During much of the series, Steed's car was a classic Bentley, which I think was more gentlemanly than the flashy, nouveau riche, yellow Rolls Royce with which he replaced it.
In various episodes, Steed was seen to drink port, claret, sherry, brandy and whisky. Of course, he popped champagne corks with style, and his brands, appropriately, were Bollinger and Veuve Clicquot Ponsardin. He drank drop-filter coffee, and was even seen to drink tea. In spite of his Englishness, I always felt that tea didn't really suit him.
His address was variously given as 5 Westminster Mews and 3 Stable Mews. The latter address is of course ridiculous, as "mews" means "stables". To get a good idea of the kind of place in which would-be John Steeds should live, visit Duchess Mews, off Portland Place. That is where the exterior shots of his residence were filmed.
Note: Mr Rich Tanner has pointed out that in some episodes, Steed does sometimes use a firearm, even in the later series in which he is much less violent than in the first two. As a correction to the above, it would be more accurate to say that Steed does not normally carry a gun, at least in the episodes with the equally iconic Emma Peel (series 4 and 5). If you wish to emulate Steed's style and character, there is still no need for gunplay, except perhaps the occasional use of shotguns for shooting game birds and clay pigeons.