Term limits should be set. I think 12 years in Congress is about the optimum number: not too long to become your life, but also long enough to get "enough experience" and pass it along to the newcomers as they come in. That would be 6 terms for House Representatives and 2 for Senators.
Of course it's not a magic bullet. Many other things need to be changed:
1) banning corporations, PACs or any organization from giving money to politicians - only individuals should be able to donate and the sum should be limited to maybe $1,000 (allowing "NGO's" and such to give money is just a loophole looking to be abused)
2) making votes in Congress anonymous [1]. Votes shouldn't have "transparency". There's a reason why anywhere else voting is anonymous: it's much harder to get influenced this way, whether it's by money or peer/leader pressure (see invasion of Iraq, passing the "Patriot" Act, etc). The lobbyists can give you money, and then you can still vote as you wish, which over the long term it will seem like a less and less viable strategy for lobbyists.
3) switching to a much more democratic voting system ("approval voting" [2] would be ideal, but even the 2-voting rounds system that's used in some European countries would be a HUGE improvement, as it would fix the "spoiler effect" somewhat - but still nowhere near enough as approval voting does)
4) proportional party representation in Congress (seems like a no-brainer to me). The idea that 2 parties can dominate Congress/Parliament for a century seems ridiculous to me. Parties should rise and fall every 10 years or so, like it happens in Europe. That would put the focus much more on the issues and much less on "being on the Red or Blue team".
5) abolishing or fixing gerrymandering
6) maybe even regulating the revolving door issue (this one is a bit tricky to do, but I think other countries have some regulation for this)
I'm sure there are many other things that can improve how Congress works. The idea is to make them listen much more to the People [3] and much less to single rich individuals and corporations.
[1] - https://www.youtube.com/watch?v=1gEz__sMVaY
[2] - http://www.electology.org/#!approval-voting/cc04
[3] - https://www.youtube.com/watch?v=mw2z9lV3W1g