Knowing which Clan tartan you should wear...

[Bluescelt]

Lindsay is a more common tartan and at the games I've been to they usually have a good selection of Lindsay items. If you are looking good for quality and fit you may want to have your tartan items made vs off the rack. You'll get a better fit and usually much higher quality too. Another good thing to do is get involved with the Clan Linsday Society.
Unfortunately in the Northeast USA they aren't very active. If you have an interest in their history sponsor a clan tent at your local games.
Traditionally, Clan Lindsay and us Donnachaidhs were were at odds but we've had quite a good time with them over the years. Many of them actually attended our annual clan dinners!

[Bluescelt]

That's right Jock. My Duncan's were from Fife and although Perthshire is not far away I'm not sure that they took the name from Donnchadh the Stout. The first Earls of Fife were named Donnchahd too. All depends how far back the family goes in an area. In saying this I guess the idea of clan is like-minded people that band together. Historically not all clanfolk were related and allegiance sometimes changed. So if you find a clan that you feel a connection with go with it. We see this at clan tents alot. Some names are commonly listed as septs for multiple clans. Folks will ask which clan they should be with. I'll ask where was your family from and if they don't know I just tell them find the clan having the most fun.