Let me see if I can add to Tim's/Lotus' manual post. Or maybe clarify. Or simplify. Or just muddy things up.
Feel free to reply and clarify. I am working from memory.
This reflects an ELISE only.
In a nutshell, this is a very easy job and should be considered as an option any time you do work on the engine. It is a bit of work done up front, that makes the other work a lot easier. With the clam off, access to everything is easy. Most of this may look more difficult, but standing in the car, doing one step at a time, it will be more apparent how easy this is. My sequence may be a little different, I like doing the in-cabin work BEFORE I jack the car up.
The main work on getting the clam off is that you have to remove the plastic bulkhead behind the seats, which means removing the seats. And it is a bit fiddly getting the cables in the grommets for the clam.
You can do this job by yourself, including the final lifting of the clam. But it is easier with someone else... just not required. Make sure you have a place set aside for the clam once it is off. Best to have some supports so that the clam is not resting on the fiberglass on concrete. At least use some padding/towels under it.
There are some tools that will make your life easier for this job. Mainly extensions for the 3/8" socket drive to get the seat bolts out... and also a long extension and socket for the nut that holds the rear window shroud sides (access from the wheel wells).
1. Take off the roof. Hardtop or soft top. Take it off. If you can't do this, then stop right here and let someone else do this job. In fact, consider if this is really the right car for you. ;p
2. Remove the two seat's fasteners. This is an EASY task. Really. You will see each seat has 4 fasteners. Some are allen head, some are hex bolts. Remember which goes where. A VERY long extension (or two) will make reaching these very easy. The driver side is easier because you can slide the seat forward and back. Probably the hardest bolt is the inside passenger rear one.
Note that the driver's side has two stops that exist to limit rear seat travel. The double stop is on the outside, the single stop next to the center console.
Set the stops and bolts in a baggie.
Note that when you re-install the seats, be VERY careful to not cross thread the fasteners. It is easy to do. If you do end up needing a tap, I have one.
3. Pull the seats out of the car. If you still happen to have the driver's side seatbelt connector connected, disconnect it. At this point they will be tethered by the seatbelt. Once the seat is out of the cabin, set it on the ground and using a 17mm wrench, remove the seat belt attachment bolt. Note the arrangement of the bolt, spring, spacer on the seat.
4. Now is a good time to do ANY work inside the cockpit, including cleaning under the seats, disposing of the french fries and anything that was under the passenger seat.
5. Remove the trim panel plastic under the rear window shroud. You can see some plastic fasteners. Remove those. Carefully.... VERY carefully pull the plastic liner under the rollbar away. It is very easy to crack this so take care. A small flat screwdriver covered in tape is always a helpful tool for working on interior plastics. Under the trim panel, you will see two metal brackets as pictured in BR.2. Remove the two M6 screws and washers. Save in a baggie.
6. Remove the rear bulkhead (the part that was behind the seats). Leave everything that is on the bulkhead (net, interior light, speakers) still fastened to the bulkhead, just pull the bulkhead away and disconnect all the connectors. You will have to pull it away from the plastic bits and carpet stuff. Set the bulkhead aside.
7. If your car has the sound deadening foam in it, remove this, carefully pulling it out from the corners so as to not tear it. This is a bit heavy. Set it aside.
8. From inside the car, remove the B post fixing (see BR.7 pic) from inside the cabin. This one is really easy. Do both sides.
9. From inside the car, remove the two bolts on each lid hinge. Note locations of rubber/washers.
10. Remove the lid and hinges from outside the car. Set aside.
11. Inside the engine bay, unhook the washer bottle and let it dangle.
12. Inside the boot, detach the battery cables. If you are anal like me, wrap the positive end in tape. Untighten the battery attachment bracket and remove the battery. Set aside.
13. Pull up the carpet/foam at the bottom of the boot. Note the two bolts on each side, one near the rear of the boot, one near the front. Remove the bolts and baggie them.
14. Disconnect the cables to the rear tail lights.
-Intermission- At this point, you have probably spent about 60-90 minutes on the car if you took your time. Your interior is gutted, the rear window shroud is almost ready to come off. Now we move to the next step.
15. Break loose the lug nuts or lugbolts on the rear wheels. Jack up the rear of the car using Jim Clayton's cool tool. If you don't have that, then jack up each side. Place jackstands under the proper points. If you are doing other work that requires bottom access, it would have been a good time to remove the diffuser and bottom panels.
16. Remove the rear tires. Remove the rear tire well liners. These are easy, just a philips screwdriver to remove the plastic fasteners. Pull out.
17. Up inside the wheel wells, almost easier to feel than to see, is the M6 nut holding the rear window shroud to the clam. Using a long socket (the stud is long) and a long extension, remove this nut. You may want to consider going in from the engine compartment. Or not. This one is a bit tricky.
18. At this point, nothing is holding on the rear window shroud except the weatherstripping. The proper method for removing is to peel the stripping back off the cover. I then used some bluetape to support it to the rollbar. But some have reported carefully cutting the weatherstripping so it comes off with the cover. I can see how a good diagonal slit would still work well once it was put together. Your call. I had some adhesive to put mine back, but I found that it was still sticky after one removal so I did not need it. In any case, pull off the cover from the clam, carefully applying equal pressure to break it free (it can tend to stick at first). Set it aside.
19. Using an allen wrench, remove the fuel filler ring. Do not remove the gas cap.
20. If you still have a snorkel, remove it and toss it.
21. Remove the two bolts that attach the clam to the sill panel (in front of the rear wheels) and air intake grills. You can remove the grills.
22. If you have not removed the diffuser, remove the bolts connecting the rear panel/grill to the diffuser unless you want to remove the rear panel/grill from the clam. If you do want to remove the rear panel/grill from the clam, remove the bolts inside the rear of the boot. These are a bit of a pain to re-install by yourself, suggest two people for this.
23. Snake the battery and rear tail light harness wires out the grommets.
24. Life clam off car. Set carefully where protected.
25. Note location and condition of chassis frame spacers where the clam was resting on. These are held on with tape and the tape can get old. I suggest marking with a sharpie how many shims there are at each of the 4 points and using good duct tape, retaping them. I used aluminum heatshield tape on my car. Worked well.
Done! This is about 2 hours of work all told. After your first time, it is 90 minutes at most.