先: before; ahead; tip; previous. JLPT N5; 6 strokes.
先 means 'first, ahead' in time and space, and also 'point, end'.
On reading: セン in 先生 (せんせい, teacher; doctor), 先週 (せんしゅう, last week), 先月 (せんげつ, last month), 先日 (せんじつ, the other day), 先輩 (せんぱい, senpai, senior colleague), 優先 (ゆうせん, priority).
Kun readings: さき, 'point; first; ahead': 先に (さきに, first, in advance), 指先 (ゆびさき, tip of the finger), 行き先 (いきさき, destination), 宛先 (あてさき, recipient's address). まず (先ず, first of all) is almost always written in hiragana.
Remember: 先生 (せんせい) is not used only for teachers, but also for doctors, lawyers and other professionals.
先に行ってください。
saki ni itte kudasai.
Please go ahead.
Follow the steps in order. Each new stroke is highlighted.
Stroke paths: KanjiVG, CC BY-SA 3.0. Sequential diagrams derived from the original paths.