When you have to get the objective "Be 34s in Fever mode", have someone (preferably next to you while your playing) call you when you just got in fever mode, pick up the phone, and wait for 34 seconds. The other person then must disconnect the call. Go back to the game and you'll see you completed the 34s fever mode objective.
You earn 10 points for every "great" slide you perform. A "great" slide is a perfect slide through a valley, where you lose no speed and get the maximum air coming out. You also get 20 points each time your bird touches the clouds after a high jump.
You can get a great slide (10 points) from your first curve by not pressing the screen immediately. Instead, wait until the bird flies just before the first trough before pressing the screen and closing its wings. This way you can get a great slide right at the start of the game.