First, mark your spawn point. This will be important in the first few days, as you will respawn back here if you happen to die.
Now, walk over to the closest tree. If there are no trees around, just roam a little and you'll eventually find one and start punching wood blocks (you do not need a tool for this).
Wood is a very important resource which is needed for basic crafting. One or two trees worth of wood blocks will be more than enough to get started. More is better, and allows you to make a larger house, more tools etc. Make sure to build your house near to the spawn point, or else craft a bed to reset your spawn point.
Do not destroy or return your bed to your inventory as this will cause your respawn point to re-default to your original spawn point, potentially taking you far away from where you were upon death.
