I have not yet chosen to affiliate with a clan, and I'm not sure that I ever will, but the whole subject is also relevant to choosing a tartan, which is something I've thought a lot about. As briefly (heh) as I can put it, here's my situation:

Closest surname with a tartan: Morris (paternal side)
Closest Scottish surname: Esplin (paternal side)
Closest Scottish surname with a tartan: Graham (maternal side)
Closest surname on Scottish soil (Dundee): Esplin (paternal side)
Closest surname with a tartan on Scottish soil (Wardend, near Airlie): Campbell (paternal side)
Closest surname in the Highlands (Braedownie): Ogilvy (paternal side)
Most common Scottish surnames: Crawford (paternal and maternal sides), Stewart (paternal and maternal sides)

Now, if I went the "Tartan for Me" route, I could claim the Buchanan or Gordon tartans, the Morris of Wales or, if it's not restricted, the Morris of Eddergoll. The problem is, I'm quite confident my Morris ancestors came from England, and from a part of England that is closer to France and Belgium than it is to Scotland, or even Wales. Wearing the Buchanan or Gordon tartans might make the most sense to someone who doesn't know my family history, but I don't think it makes any sense for me (although I do have some Gibsons and Buchanans back there).

There is, of course the purist (non-)option: I'm an American, and one of English lineage, so I have no business wearing the kilt (except, perhaps, as a member of my pipe band).

With the Esplin surname, the "Tartan for Me" route (inexplicably, as far as I'm concerned) recommends the Stirling tartan rather than the Angus. The surname is not associated with any clan and has no tartan of its own, although that could be remedied.... If there was an Esplin tartan, I would most likely choose to wear it.

Going by MacMillan of Rathdown's recommendation, I think the likely choice would be Campbell. I have sort of gravitated towards that clan, but have not chosen to join its society so far. I would like to know where my Campbell ancestors fit in. Did they spring from the Glenorchy/Breadalbane branch, as geography might suggest, or from another branch of the clan? Unfortunately I've hit a dead end at Brydestown (almost undoubtedly the modern Braideston), Forfarshire, in the mid-18th century.

Another thought: Many of my more recent Scottish ancestors (including the Esplins) lived in Ogilvy territory. If they had any sort of clan allegiance, it might have been to the Ogilvies. And, as I mentioned above, the closest ancestor I can actually place in the Scottish Highlands was an Ogilvy.

So, anyway, my provisional decision has been not to join any clan association and, as for tartans, I think my first wool tartan kilt (apart from my band's Inverness, modern colors) will be in the Angus tartan, muted colors. No divided clan loyalties to worry about. (But now are there district rivalries to worry about? ) The recently-designed Strathmore tartan would be another option, but I prefer the muted Angus.

Now, will this post help anyone else make a decision about what clan to join, or what tartan to wear? Who knows? *shrug*