Well you know how If it's a strong Acid you'd use Methyl orange right? Well personally, Orange juice (The actual juice of an orange) tastes quite sour right? so like acidic right? So you can instantly realize, "Oh Strong acid, Hmm methyl orange"
And then for the Phenolphthalien i would just use a process of elimination , so then we know its used for a strong alkali!
Sorry if i don't make sense! |:
good luck for your exam! xD