1. Play stages mostly unfocused and stay unfocused.
2. When an enemy comes out with familiars, switch momentarily to focused to take them down, then unfocus againafter they're destroyed. Focus won't hurt the familiars, so you'll be able to eliminate the source and get bonus time from the familiars self-destructing, plus clear away a crapload of bullets at once.
3. During bosses, pretty much stay focused all the time is my advice, or almost all the time. Staying one or the other is the recommendation.
4. Aim to capture spellcards and not die/deathbomb, because the latter will incur time penalties, but capturing cards adds notably to your time.