There is no magic. Lose weight. Climb lots. You will get better.
Forget about your buddies flying past you. When the hills show up, shift into a comfortable gear and just spin your way up. Do not think that you can push a big gear, pedal real hard and fly up the hill.
I think everyone has already outlined all the key points. In my case, I'm 205, 6'3". In real world standards, I'm lean (six pack, big legs etc I used to lift weights quite a bit). In cycling standards, I'm big (huge, a clydesdale etc etc). All basically saying that you will succumb to the laws of physics. I don't race, but I rarely get passed on climbs. I put a lot of work into:
1. pedaling at a higher cadence and trying to maintain that up hill (speed be damned, just be consistent),
2. Climbing as many hills as often as I can.
3. Doing more leg work last off season.
When I do get passed, I shrug it off, stick to my own pace to keep from blowing up. Some other short tips, work on climbing sitting most of the time except when the climb is short and you are familiar with it, in which case you can stand and power up it. Funny thing is that until you get familiar with the proper technique of climbing standing, your speed/cadence will drop, your heart rate jumps and you tire/blow up .. and this is what many think helps. It does help to mix it up a bit on longer climbs but do it only to rest your lower back.
I imagine some of the same may work for you (save the vast physical/physiological differences that I'm sure exists as you are not my twin).
For a more wordly example, look at Hincapie. Someone asked him how he improved at climbing; he wasn't bad to begin with. But his response was that he climbed every mountain he could find many times and was really focused on his diet/weight loss. I'd take this as gospel from a fellow clydesdale (sort of). Hincapie is 6'3" and 176 lbs (was about ~185 lbs). Now imagine him strapping a 20 - 30 lb bag on his back and trying to do the same thing. That's the equivalent of someone like you or me trying to climb with someone 20 - 30 lbs lighter. And yes, I know he puts in way more training than you or I.
I don't much care about wattage, but cadence & heart rate are my guides.