Oil & Oil Filter change.

[darrsi]

I personally use a ring spanner, it's a bit easier to use with the bike on the side stand (drains the oil easier on the side stand).
Undo the bolt first, making sure the oil is directed into a bowl correctly, then undo the oil filler cap to let the air pass through.
Then tighten the bolt back up firmly but not overtight.

Then put the bike on the centre stand on a flat surface before refilling with oil.