Don't forget to spend 5 - 10 min to warm up your drawing muscles before you start working.
https://www.youtube.com/watch?v=hSaXBVYVcQg
Here is a playlist with more ideas
https://www.youtube.com/watch?v=1weuSynPkbY&list=PLQIV4DB0RUNcKiXO_PYUfhjrPxhHUwwxt
You can of course devise your own exercise routine - do you need to practice brushwork, a certain delicate line, boxes, texture, colour, gesture, imaginative drawing? Include it in your warm up routine.
https://www.youtube.com/watch?v=hSaXBVYVcQg
Here is a playlist with more ideas
https://www.youtube.com/watch?v=1weuSynPkbY&list=PLQIV4DB0RUNcKiXO_PYUfhjrPxhHUwwxt
You can of course devise your own exercise routine - do you need to practice brushwork, a certain delicate line, boxes, texture, colour, gesture, imaginative drawing? Include it in your warm up routine.