I used to live there and I work ther one day a week.
My suggestions are:
1) Novotel or Ibis at La Defense. The latter is more reasonable but the rooms are pretty basic. Perfect if you intend on spending your time out and about and just need a decent base. The rooms are quiet, have AC, TV with english channels and La Defense is a pretty good base from which to see paris with. I always stay at the Ibis.
2) Any of the smaller hotels in the 5th/6th Arrondissement (St Germain). They are cheap and very close to all the tourist traps. It is also in the party area so can get noisy but if you want to stay out late and have a raucus time it is ideal. Good ammenities and shops but these hotels are cheap for a reason. No AC, noisy and often very tired.
3) Montparasse area. Middle ground in terms of cost but farthest away from the tourist sights. Can vary a lot in quality as well. Make sure you check on tripadvisor before you go.
4) Montmatre. Very touristy but more arty and bohemian if thats your thing. Cost/quality about the same as St Germain. Be very careful about choosing your hotel here as the 17th arrondissement is a no-go area for tourists.
Suggestions on where to go:
Arc de Tripomphe and Eiffel tower - get there early when the queues are shortest.
Louvre - if you are not in to art/history it can be a bit tedious. There is some very famous works here though so if you like this kind of thing you will enjoy it. I found the Guimet Asian Museum in the 16th arrondissement fascinating, it has some rare artifacts that survived the Taliban's eradication campaign and houses some of the only specimens of blue glass for which Afghanistan was world famous (while we were in loin cloths Afghan was super rich because of this trade)
http://mentalfloss.com/article/48954/recreating-1900-year-old-glass-fishJardin du Luxembourg. Easily the best spot for a walk with the missus. Trust me, just go.
Paserelle Debilly (footbridge between Pont de l'Alma and Pont d'Iena) best corner view on to the Eiffel towel. Great at night when the tower sparkles on the hour.
Champ de Mars/Ecole Militaire - I used to live in this area and would often have a picnic at night on the grass. Great atmosphere and view. Tip: a photo of the Eiffel Tower through the peace wall is a great shot. I have a few that I did one night.
Rue Cler - A fairly traditional french street with lots of good shops for all things food and wine. Sunday morning is market day there and the only place you will see the french working on a sunday. Le Cafe de Marché is one of my favourite places to eat, the maigret de canard with garlic potatoes is the best I have ever eaten.
Avenue de Suffren/Bde de Grenelle market (Saturday morning) - a general market selling, food, cheese, wine, good quality antiques (not like the flea market sh!te), clothing, etc. Worth a look if you like that kind of thing.
Things to avoid:
Any resturant where there are people outside trying to entice you in. Regardless of how good it looks or how hard the sell just think 'What kind of decent restaurant needs to pull people in of the street?' That's right, none. Go where there seems to be plenty of Parisians or even better where there is no sign outside and some obnoxious old git waiting on the tables, the service will be crap but for food they are often the best. If you have the budget I can heartily recommend Chez Paul 13 Rue de Charonne in the 11th arrondissement. Not the cheapest (not exorbitant either) but worth every penny. You may even be sat at a table next to some celebrity as it is very popular with the likes of Jean-Paul Gautier et al. Their steaks are the best but budget around 30-40€ a head including drinks but their meat is delicious, even the bog-standard piece of beef in bernaise sauce is mouth-watering. Warning, they can be picky about their clientel if you go there dressed as slobs you wil be turned away. Oh and make sure you book ahead of time.
The 17th and the Western half of the 18th arrondissement. Crime hotspots! These places are often off limits for Parisians, tourists are easily identifiable and easy prey.
Pickpockets. There are lots here, especially on trains and the metro. Even I have had my run-ins with them so dont think being big or mean will deter them. Common tricks are the distraction method at the ATM/your bags/pockets and watch out for anyone too close with a coat over their forearm held at chest height. THink, who the fleck carries a coat in summer? Answer: pickpockets.
Giving money to beggars. Remember this is a very socialist country and the homeless are relatively well looked after. Most beggars regardless of how bad off they look are often part of organised Romany gangs who take the money home and build huge mansions with the proceeds. Thus, please dont feed the pigeons!
Right that's enough sensible talk! Back to fart jokes and exploding garages........