I think best way is to just go to Services and join open campaigns . for bounties there is a section for bounties too. to join a good bounty just check which bounty token is listed in exchanges then join it.
However if we were talking about new campaign.. Then you must activate the notification on the both sections so that you will be notified when there's a new campaign from them.. But these days it's very hard to find mate, where in sometimes within a month there's no new campaign . So much better to visit their profile to see if there's an existing project with an open slot if you want a quick opportunity.