Adding variety to my campaign is important to me as a DM. I want each live session to be unique in some way. Lucky for me, I have a group of enthusiastic players who are willing to be frank with me as we plan out a long (two consecutive years now) campaign.
Here are a few ideas from my campaign to yours that you might discuss with your group.
The setting for your campaign can make a huge impact on what you do. We use the massive metropolitan setting of Ptolus. In one place we have dungeons to crawl, manors to infiltrate, mountains to climb, seas to sail, and skies to fly. We love it. Regardless of whether you use a commercial setting, encourage your DM to switch up the terrain at least every other game to keep things fresh.
Confronting the crew of an opposing airship 400 feet apart and 1,000 feet in the air makes for a very different game than a "typical" dungeon crawl, and invites different tactics. Seeking diversity ensures that every character has a moment to shine.
There is already some great advice here on this subject. Variety in the tactics of your foes, coupled with non-combat challenges during an encounter give more characters a chance to shine. This takes preparation. Preparation takes time. But if your DM is willing to invest it, the payoffs are sweet.
I thought I was an imaginative DM. Then I met the incredible writing of Monte Cook and learned I merely had delusions of adequacy. I'll tell you, whether it's a few bucks on a single module or an entire campaign setting, the ideas that come from 3rd-party publications pay off long after the material is exhausted. If you don't do this already, consider offering to buy a module and loan it to your DM.
As a DM, I'll grossly understate my involvement to say that prepping for our game takes A LOT of time. Making a great game with interesting tactical situations usually does. If your DM also hosts the game, offer to take that off his or her hands to buy more time to prepare. The gesture will be appreciated and the games would likely benefit.
Sometimes, every last person at the table has put time, heart, and soul into things and the game still falls flat. It is always a good idea to be patient, grateful, and understanding if a session or two don't meet our expectations. Be open with your DM about the things you enjoy, and in time things will perk up.