Well, one of the first things one runs into when trying rosary making, are the imperfect loops... that is, when you're making the second loop of an eye pin after putting the bead on, trying to make a nice loop after it out of that strait pin.
Practice makes perfect, but here's a couple tips... holding the ready-made loop so that it's flat (horizontal) between your fingers, after you put the bead on, use the fingers of your other hand to hold the bead against the ready-made loop, and bend the straight or open side of the pin so that it points straight down, or even so that it's bent back in a little toward the ready made side. You want to end up with the ready-made loop still straight out (not bent down), so be careful.
Once you have your open side bent straight down, the bead isn't going anywhere. Now you can worry about making that perfect loop. You should be able to make a great loop virtually in one motion. You're going to grab the very end of the straight or open side, and aim to twist it around the tip of the pliers... basically, using the pliers tip as a 'mold' to shape it. That's probably basic, but... HERE is the pointer:
Find the sweet spot on your rosary pliers!! Before you get started, take your pliers (presuming that yours have a perfectly round tip... no flat side on the inside), and stick the tip of one side through the already made loop of one of your eye pins. See how far down it slides? That's approximately the "sweet spot" or else it's a microscopic fraction above it. Theoretically, if you grab the open side about that far down on your pliers (or a smidge lower) you should be able to twist it up, and with virtually one smooth motion, get a perfectly molded loop that more or less matches the first.
So what you're doing is, paying close attention to how far down that straight pin is between the tips of your pliers when you go to make your second loop. If you grab it in the right place... that is, with the pin just far enough down between the tips, but not too far, you should get a loop that is perfectly formed and about the same size as the other. It takes practice, but this is what you're looking for if you want to make virtually perfect loops.
By bending the pin down like I said, you're cutting out the task of having to fix or bend down the loop you made in order for it to be even. If you don't bend it first, your pin will naturally end up in the shape of a lower case d laying on it's side ... flat with an upwards loop. If you bend the pin down (or even a tiny bit farther down/back than that) when you finish twisting the pin into it's second loop, that loop should line up pretty much in the center with the hole in the bead (more like a lollipop than a d). AND... if you hold the bead so the ready made loop is horizontal, the loop you form should end up vertical... thus ideal for the naturally linking pattern of the rosary.
Grabbing the pin too far up the tip of your pliers will result in what I affectionately call a "lemon" ... a midget loop or something generally misshapen. Grabbing it too far down will make the loop too big. Also if you grab it too hard, you will mar the pin! These things become second nature with a bit of practice.
To get it closer to one motion, rather than grabbing the tip like you want to naturally, twist your wrist so that you're grabbing it "upside down" (or opposite the natural way). That twist of your wrist turning right side up SHOULD be enough to make a complete, or near complete loop.
OTHER TIPS:
When you're putting the crucifix on, I find it necessary often to adjust the number of links between the Our Father bead and the crucifix, in order to get the cross to lay flat (facing the same way naturally as the centerpiece does, without turning sideways). I think it's the best form to make sure the cross naturally hangs straight forward along with the centerpiece, and not turning to the side.
When you've finished making the whole string of decades for the main part of the rosary, hook one end to the centerpiece (with an o ring... a little metal ring) and then hook a slightly open o-ring through the other loop on the centerpiece... open just enough so it won't fall off easily, but so that you can easily hook the chain through. THEN... hold up the rosary by the centerpiece. Let the string of beads hang completely loose in the air, without touching anything. When it stops spinning or swinging, take hold gently of the first bead from the centerpiece, and, continuing to let the string hang in open air, run your fingers straight down the string, in order to work out any kinks or twists in the chain, and to straighten the string of beads and chain completely. You can repeat once or twice if you want. For the final time, when your fingers get to the end of the string, hold the string just taut (by the centerpiece and last bead of the string), until with as little twisting as possible, you bring the end around to the centerpiece, and slip the chain (hopefully straight) through the open o-ring and close it.
This is how you get a rosary that doesn't twist up or kink all of the time. If you have a rosary that does, you may be able to fix it by doing this. Kinks are often caused by a twist somewhere in the chain... and with nowhere to go, that twist can lock up or twist up the beads.
In a repair, when you end up with two open ends attached to the centerpiece, you can do this by first joining the open pieces together with the repair, and then unhooking one side from the centerpiece, and following the steps above.
... Sometimes I wish I had a web cam... it'd be much easier to show this than explaining it!