Faustregel — fist rule. A rule of thumb.
Erfahrungswert — value of experience. A figure that is not calculated but known from practice.
aus dem Handgelenk — from the wrist. Done without preparation by someone with practice.
Gespür — a feel for something. Ein Gespür für die Situation haben, to have a feel for the situation.
abschmecken — to taste and adjust. German recipes often end with mit Salz und Pfeffer abschmecken, season to taste with salt and pepper. The recipe gives the frame, and the cook decides the amount.