1. Tighten from inside out and bottom up! When you engage your core muscles (starting with a squeeze of the pelvic floor muscles, then recruiting the lower abdominals), you can visualise your strength growing from the inside out and spiralling upwards. You can do this even from sitting (waiting for traffic lights to change, for example).
2. Stand tall and notice your breath! If standing in a queue waiting for somebody or something, practice standing tall and watching your breath. Elongate your spine by lengthening up through crown of your head. Feel even weight on both feet, lift your sternum and bring shoulder blades a bit closer together at the back, allow your arms to relax down by your sides. Gently draw your lower abdominals inwards and upwards a bit, towards your spine. You will look taller, your heart will be lifted, your waist will reappear and your stomach will look flatter. Then lengthen your outbreath slightly; just notice the breath flowing back in. Stay with the breath just watching it coming in and out, like waves at the shore.