I have to second the flylady. She is great. Some ideas (borrowed from her.) Start small, so it isn't overwhelming. It sounds like the mail and/or the pantry are the two big places to start. I bet you could go through your whole pantry in less than half an hour if you set a timer! I know -- I just did mine last week. I found several cans of soup/veggies that were several years past their expiration date -- pitch them. Things that are still good but you bought for that recipe you're never going to make - give them to Loaves & Fishes, or some other food pantry. Then, think of 5 meals you can make using up the stuff that's still in the pantry. Use those meals to make the next grocery list. You will have cleaned out half the pantry with those 3 steps.
For the bathroom -- I too buy way too many products. I carved out a small space in my linen closet, where I have put all the duplicates/extras/experimental products. I have committed to not buying any new cosmetic/hair products until I have used up the current collection -- it could be 2 years at this rate. But, I only have one of each type out at a time now, so they are easier to see and use, and I have noticed that I have actually used up a couple of things (lotions, spray in conditioners) because I only have one thing like it out at a time now and I actually use it. I probably still have too many things on the counter, but 10 bottles down from 45 or so seems pretty managable to me.
For the mail: I put a brown paper grocery bag in my recycle bin in the garage. When I bring the mail in, I stop in the garage and pitch all the junk mail straight into the recycling. It never makes it into the house. For the rest, I have a stand up paper sorting thing (office max/office depot/target.) Bills go in one slot. Things I want to save go in another. Things that need action but aren't bills go in a third. Then, when I'm doing bills, I just grab the pile and finish them off.
We have a corner of our kitchen counter that must have a paper/mail magnet in it. It is the spot where this stuff grows and breeds overnight. I need to make a conscious effort to keep it under control every day. However, with a system for where to put things, I can move them out of this spot pretty easily. Also, I have learned to let go of more. Most junk mail will come again -- if I might want the name of that furniture reupholsterer or whatever, I dont keep the mail anymore. I either plan to google it if I really want it, or write it down at the back of my calendar, or just let it go. It takes time -- don't get overwhelmed. Just do 15 minutes at a time and then stop. You'll be surprised what you can do in 15 minutes!