Best strategy: Don't sell unless absolutely necessary.
Buy whenever possible and hold.
Resist the temptation to waste your bitcoins by buying fiat currencies just because the price went up. Be strong.
Do not deviate.
More like: Don't sell. Period.
Whats that? Your brother needs an operation? Not as much as I need 100k per Bitcoin. GTFO of my Lambo dreams.
What I meant was: don't sell unnecessarily for mere fiat "money".
Buying medical services or retirement homes (or fine foods or beverages... maybe even hookers, Lambos, and blow, depending on your tastes) is Bitcoin well spent, as is discharging all debt.
Selling bitcoins to bank dollars (or euros or pesos, etc.) is just plain stupid, although many people do it.
Keep your profits in Bitcoin.