Put a drop of super glue on the knot.

There are no special techniques for knotting different hole sizes however you could consider using bead caps which may be used to cover up part of your bead due to an imperfection, or a larger hole. Oftentimes, the bead cap is used to "dress up" a bead, crystal, stone, or other type of bead adding a touch of elegance to your bead.  To view our selection of bead caps, please follow the link below:
http://www.artbeads.com/silver-components-bead-caps.html

It’s important to use the right tool and the right crimps. We recommend the sterling silver and the gold-filled crimp tubes for the best results. A specialized bead crimping tool is the best to use.

Here is a link from our Learning Center on how to use a crimp tool:

http://www.artbeads.com/howtousecrto.html

For more information about this question please visit our blog:

http://blog.artbeads.com/category/ask-bailey-beader

I generally use 28 gauge as this is the easiest for me to work. But, I have used other gauges, depending on the project. It takes a little more effort to crochet using something heavier, but it can be done. I did a cuff bracelet and a pendant using 26 gauge and they turned out fine, but you don't have as much control over the wire.

The chain you use for an anklet depends mostly on the design that you are planning. If you will be dangling charms off of the chain, you may want to consider a cable chain with larger links (5mm or above) that will provide plenty of room for the charms but still have large enough links to be distinctive. If your design focuses solely on the chain itself, you may want to use a large, uniquely shaped chain that will draw attention to it.

You could use an endcap to finish leather cording. The endcap will have a closed ring at the top, which you can attach to the clasp with an open jump ring. You can see a picture tutorial of how to use an endcap in our Learning Center via the following link:

http://www.artbeads.com/finish-leather-and-rubber-jewelry.html

Sorry you have had trouble !
My experience - I can usually follow a stitch from a book, or as you tried, to consult with more than one resource. I will Google the term for additional sources of instruction for the stitch, going to online retailers such as Artbeads and others that now host video tutorials.
If Im having trouble after trying on my own, I break down and attend a class at my local bead store. If your ' local' doesn't offer classes, ask the owner for references for a live tutor. If you don't have a local bead store .. try nearby towns and make a day or week of it to get access to some hands on training.
If all else fails - be honest with yourself and move on. Theres a likely sister-stitch that will give you a similar result to a stitch or technique you just can't get your head around.
best beady wishes - Laurie

6mm being about 1/4" to 1/5", you could likely use one of those tiny Keyring circles about 1/4" to 5/16" in diameter.
Another way would be to find a bead of neutral or complimenting color, with a hole in the center that would fit the thong, that has an hour glass sort of shape, and wrap the silver wire around it attractively so that it is horizontal.
Or...
Use slightly larger wire, say, about 0.050, and hardened if possible, wrap the head, then at the "tail" of the head take the wire and wrap around a 1/4, or 9/32, or 5/16 Pin Punch held perpendicularly to the axis of the arrowhead, about 4 times, head back toward the arrowhead, then holding the head and using the pin punch as a handle while still inside the wire, twist it around once or twice to suit. hide, cut, and file smooth the end of the wire. Then lube the pin punch and work it out of the twisted loop carefully. (In fact, perhaps you should polish and ever so slightly taper the punch first.)

Crimp beads and tubes are the best way to secure beads on jewelry wire. A basic pair of crimping pliers such as TOOL-100 is a worthwhile investment.

http://www.artbeads.com/tool-100.html

Here is a link to one of our videos that demonstrates step by step on how to crimp:

http://www.artbeads.com/crimp-tube-ht-video.html

For more information about this question please visit our blog:

http://blog.artbeads.com/category/ask-bailey-beader

Store your silver findings in the small plastic bags and keep them out of direct sunlight.