Most of the previous advice is pretty good.
If I was to make that antenna, I'd first solder the double loop up with a small butane torch. Then use a soldering gun (the big ugly ones that should never go near a circuit board) to make the final connections to the connector.
Use 'helping hands' to hold stuff on place.
After assembly, use some silicone sealer to stabilize the joint mechanically.
The point about dimensional accuracy at 900 MHz is 3 times as important at 2.4 GHz; a fraction of a millimeter is important here. Unfortunately, you likely do not have the equipment to measure the results, so just be as careful to be as precise as you can.
By the way, if you want a
directional WiFi antenna, I wrote an article on that, see
ftp://ftp.tapr.org/psr/Autumn_85_2002.pdf on Page 8. Let me know if you ahve any questions on that.
Don