Program your shift keys, so you're not reaching for the finicky soft keyboard each time you want to use logs, trig functions, calculus, etc.
If integrating a trig function with a constant, take it out first always. Calc will sometimes freeze or crash ('!' mark in the flashing 'calculating...' box) depending on how complex the expression is, always try and simplify it as much as possible for the calc. In addition to this, you also should take out any constant since the calc can decide to go rogue and give you a dodgy answer which you will have no way of knowing in the exam.
tl;dr: classpad is a piece of crap and we need to do our best to work around its shortcomings.
That's from my experience, as for techniques I'm guessing by using it for at least 2 years you already have all the essential tricks with you. (know how to find inverse, judge, etc.)