Okay - here is what I do and I'm no professional but really as it was pointed out, if you do a bit now - you'll save a lot of work later on.
1. Most important - wash your car regularly with car soap. NOT dish detergent (palmolive, dawn etc) as this will strip the wax and finish off your car. It's fine if you want to start from scratch and wax after that but I don't recommend it - ever. Anything will work here really, armor all, turtle wax, mother's. I buy whatever is cheapest and on sale.
2. Wax. And Wax again. Then wax some more. It's the simplest and easiest way to keep your paint looking like new for years. If you are truly lazy, then yes, something like Nu Finish will be good for several months at best (depending on where you live, whether you garage it or not etc). Apply this wax to every painted surface - mirrors, A / B pillars, roof, alloy wheels (yes I'm serious) etc. Do this a minimum of twice a year - once in the spring, and once in the fall. More if you feel up to it and have the time, you could do it monthly or quarterly. Always try to wax in the shade!
3. Interior / tire dressings. This is the part that separates the men from the boys in my opinion. Here's what I do: for my tires, I ALWAYS use a degreaser to get brake dust and grime off my tires and wheels. Simple Green or Spray Nine work perfectly here. You can also use it to clean spots on your carpets, get stubborn stains off your rubber floor mats, whatever you want really. Wet the tires, spray on, you'll see it start removing brown gunk immediately, scrub with a DIFFERENT sponge than the one you wash with, and clean the alloys, then rinse. Now go wash the rest of the car. When its all nice and dry, apply a tire dressing. People have lots of opinions here but for me, I like shiny. So I just use Armor All. Works great, always has and I have no issues. If you want something that lasts longer, 303 Aerospace Protectant is your friend but its pricey. There are lots of other options out there but as I said, I use Armor All and buy the big jug whenever its on sale.
For the interior, just vacuum and use a slighly damp microfibre cloth to wipe down the interior dash, panels etc. Use the same cloth to wipe the insides of the windows. Windex / window cleaner is really not needed here. If there is anything really bad on the dash or elsewhere, get out the Simple Green or Spray Nine but plain old water works perfectly for most of the jobs and doesn't leave streaks (assuming you do this in the shade!). Once that's done, use the armor all / other interior protectant and apply it to the dash, door panels etc.
5. Leather cleaning / maintenance. Here's where I'm going to give you a lesson in leather. First off, it's a natural product (usually) that requires MORE maintenance than cloth. Why? Like your own skin, leather has pores in it. These pores can become clogged with dirt and oils. You need to clean them - even when new. Most modern leather has a clearcoat to help protect it but the fact is that just sitting on the leather stretches it and creases the leather. Unlike your own skin, leather does not have anyway to replenish its oils to keep it soft and supple. Therefore you have to do it yourself.
What do I recommend? There is NOTHING better (and don't even bother using anything else) than Leatherique. Go to
Home Page | Leatherique Restoration Products or
Leatherique Canada to see for yourself! Disclaimer - I don't work for them or anything, I'm just a believer in their products.
Ok, so assuming you buy this stuff, what you need to do first is give it a good cleaning. For that you would use the Leatherique Rejuvenator Oil. Apply this when its hot and sunny outside so you can seal up the car and the oil can penetrate the leather. I apply it liberally by hand but a spray bottle with a soft cloth will work too. You will need to do this once a year probably, depending on how much you drive or climate etc. Hotter climates will dictate doing this more often. I live near Toronto and once a year for our car (which is outside 100% of the time) is plenty.
Next, you need to soften the leather. For this you use the Pristine Clean. Yes, you use the cleaner AFTER the oil. Why? The oil pulls the dirt out of the pores and brings them to the surface. It will be sticky and gross after sitting in the sun for awhile but the pristine clean will get rid of all of that. Apply with a spray bottle, wipe with a clean cloth. You will need several cloths to do an Odyssey properly.
Finally, if you are super OCD and want the leather to look a bit shiny and clean (vs matte), then you can use the interior protectant / armor all on the leather. This will give it some UV protection as well so it will help avoid the cracking and fading.
That's it! I would suggest that if you did all of the above twice a year, you'll have a very nice looking Odyssey for many many years to come. It's also a great time to check for scratches, dents, paint chips etc and you'll be amazed at how great it looks after you're done.
Good luck and I hope that helps!