It is hard to give a step-by-step guide to making your own Pandaman. There really is no “best part” to start with. Just pick a body part (such as the legs or arms) and work your way through each of them in turn. Keep in mind that you will have to assemble the parts into a whole at the end and that some parts might be harder to reach.
You may have to reach into the body to put on the final pieces (such as the head, the limbs etc. You can cut into the base to make this easier and later cover up the cut with a piece of tape. Since Pandaman sits on that part it should not be noticeable.
If you happen to come up with a method that works especially well for you, feel free to drop Ndbag a line via the contact page. ^_^;;;

Paper is an amazingly resilient medium and can take a lot of abuse. It can also bend and even “stretch” to a certain extent. Gentle, but firm pressure and/or tugging into place will give the best results.

Cut along the solid lines to get the individual pieces. It is a good idea to gently score along the dotted fold-lines in order to make the paper bend easily into shape. Be careful not to apply too much pressure, so you don’t cut the paper all the way through. In some cases some of the flaps might overlap a bit on the printout. This is generally not a problem. As long as you retain some of the flap, you should still be good to go.

In general, the placement of the flaps will give you an idea of how the pieces fit together. You might have to assemble a piece to see how the next piece might fit onto it. A good rule-of-thumb is to work “inward”. For example, start with the foot and then work your way up the leg. Thus you can reach into the model to apply pressure to the flaps as you glue them on.

If you are using a laser printer, you might notice that cutting along the lines might produce some fine dust. For best results, wash your hands before gluing and wipe your work-surface frequently. Otherwise the glue might discolour the model slightly.
If you are concerned about health issues relating to fine dust and/or the toner used in laser printers, you should probably not use a laser printer for this project.