Seated forward bend actually used to be one of my most hated poses. When you're just developing a yoga practice(myself included) people often want to get into the cool stuff like headstands! holding your plank for ten minutes! and all that fun stuff...which is great too, but you can also get some great benefits out of some of the basics.
Seated forward bend calms our often OVER stimulated sympathetic nervous system and activates the UNDER stimulated parasympathetic nervous system. With a society that moves faster than we can process, there's barely enough time to rest and digest with the parasympathetic system, since we're always working our fight or flight sympathetic system.
Start by sitting with your legs out in front of you, make sure that your sitting bones are placed directly on the ground to give yourself a good base. You can also place a folded blanket underneath your buttocks to heighten your base. Elongate the spine from your tailbone up to the crown of your head, inhale your arms up over your head, palms facing in towards each other and as you exhale reach towards your feet with your hands. DO NOT LET YOUR BACK ARCH.
If you start to feel an arch in your upper or lower back, retract your torso. Use your breath to inhale and elongate your spine and with every exhale try to reach your palms a little bit further down the side of your legs. Eventually your palms may reach your calves, your ankles, then the soles of your feet. It's important to also make sure YOUR KNEES ARE NOT BENDING as you're moving forward. Allow your head to fall over your thighs and take deep breaths as you start to stretch the length of your hamstrings (and calm that nervous system!).
Try and practice this one daily. Seated forward bend is great for calming your nerves after a long day, or to give you a relaxed mind state at the start of your day. Be patient with yourself and your practice, and you will slowly start to feel the changes in how your body can move.