Tripod and manually focused. Get as close as you can without him running away. Get your lens zoomed in, composed the way you want, and auto focused. Switch the lens to manual and live view. Using the magnification on the LCD zoom in (magnify) the spider. Very slowly adjust the focus to get that final tweak of the focus on the spider. Adjust slowly as the LCD will be just barely behind what you're doing with the focus. While still in live view use your remote or the cameras timer release to take the photo.
Couple missed items. Make sure all points on tripod are tightened down before shooting. Shoot in live view to reduce vibration - no mirror movement.