First, get a web-stressing tool like Neoload.
Model a number of user activities and bias your test to correspond to predicted user patterns, then scale load up as you see fit. Running queries against the database and measuring response time tells you nothing about user experience. Rather, by modeling user activities, you can gauge exactly how your server/system will respond under real load, as that's what you'll be generating.
User activity modeling can get pretty complex, but good stress tools like Neoload let you closely model the exact behavior of any machine hitting your server. Ideally, you would craft network traffic just as you would normally, so make sure to hit your load balancer if you've got one.
