My goal in all painting and wallpapering work is to reduce, reuse and recycle to the fullest extent.  I avoid bags and plastic, wash all equipment rather than throw things away, remove excess paint from trays, brushes and rollers before washing, and re-use masking tape. 

Cans are left to dry before disposal.  I also use zero to low VOC paint wherever possible, and only use oil based products if the client insists or the job requires it.  When asked how an eco-conscious painter can use 'toxic' materials, I respond that with conscious intent I replace the person who wouldn't care half as much