Stretches

Stretch warm, most days. That is how you get flexible.

The rule

Frequency beats duration. A little most days beats one long session. Around ten minutes per muscle a week.

Warm up, before a lift or run

Leg swings10 each way
Walking lunges10
Hip circles10 each way
Arm circles10 each way
Bodyweight squats10
Keep moving, no holds.

Stretch, after, when warm

Floor

Kneeling hip flexor30s each side
Figure-4 glute30s each side
Thoracic twist30s each side

Standing

Hamstring fold30s each side
Standing quad30s each side
Calf on the wall30s each side
Doorway chest30s
The spots cycling, running and pressing tighten most.

How to do it

WarmNever cold. After a session, or a few minutes of the warm up.
Hold30 seconds each. Breathe out and ease deeper. Mild tension, never pain.
OrderDynamic before, static after. Long holds before training dull your legs.
DailyHips and hamstrings every day, the full set after each session.

Sources: The Conversation, Huberman Lab, Roadman Cycling.