I think it's rather easy to find out an order to watch the series. I take the Enterprise series and the new Star Trek movie as being an alternate universe. This is because of the events of First Contact would have altered the future even if they were small changes. The fact that TNG crew made contact with key figures that would shape the future and exposing them to future technology started a chain reaction of an alternate universe. Events in the Enterprise series shows signs of this alternate universe i.e <PERSON>'s speech clearly showing the <PERSON> from First Contact and not the missing one in space from TOS episode. The destruction of Florida in ENT which I consider to be quite significant like the destruction of Vulcan in the new Star Trek movie has no mention in future canon in TOS, TNG, DS9 or VOY which makes me believe it did not happen in their version of the past. 837
The events of the crew of ENT on board TOS enterprise is not their own future but an alternate future for them which is in fact the time line of TOS. Therefore I do not include ENT in the canon of TOS, movies TNG, DS9 and VOY but as the start of the alternate universe that leads into the latest movie.
When <PERSON> and <PERSON> travel back in time in the Star Trek movie i think they not only go back in time but also to the alternate universe established by ENT. This would account for the technological differences to TOS. Obviously further changes to the time line are made during the movie. Also Captain <PERSON> is mentioned in this movie when the future <PERSON> and young <PERSON> meet <PERSON> which strengthens the ties between ENT and the movie being from the same alternate universe. The external design and interior of the USS Kelvin more closely resembles a future looking ship of the USS Enterprise from ENT than a past ship of TOS.
You could also go as far as saying that a more technological alternate universe was started during the movie "The Voyage home" when <PERSON> provides the information for warp speed on the computer. This could have sped up the development of future technologies by decades.
In conclusion I therefore watch
* TOS (TV)
* The Motion Picture (Movie)
* Star Trek Movies 2-6 (Movie)
* TNG (TV)
* Deep Space 9 (Start after the 5th season of TNG and watch them along side each other) (TV)
* Voyager (Start right after the end of TNG and watch along side DS9) (TV)
* Generations (Movie)
* First Contact (Movie)
* Insurrection (Movie)
* Nemesis (Watch sometime in the second season of Enterprise) (Movie)
If I am interested in following the alternate universe I only watch
-First Contact (Movie)
-ENT (TV)
-Star Trek (Movie)
or
-Movies 1-6
-Generations (Movie)
-First Contact (Movie)
-ENT (TV)
-Star Trek (Movie) 837