Which set of instructions is more formal?
Wash hands, utensils, and work surfaces after touching raw meat or poultry. If you're going to be touching raw meat or poultry, you'd better wash your hands, forks, knives, and cutting boards afterward.
Informal writing is typically used in casual situations or when communicating with someone you know well. Informal language often expresses familiarity and tends to sound more like speech. It uses more conversational language, such as slang, idioms, abbreviations, imprecise language, and contractions.
Formal writing is typically used in academic and business writing or when writing directly to an authority figure. It tends to be more courteous and impersonal, avoiding overly familiar or conversational language.
Compare the following sentences.
Informal: Yeah, ostriches can't fly, but I think they're awesome.
More formal: Ostriches may be flightless, but they're remarkable runners.
Most formal: Though flightless, ostriches are remarkable runners.
The second set of instructions is more formal. It uses more impersonal language and a direct command (wash utensils). The other set of instructions uses more conversational language (if you're going to be touching, you'd better).