I have written about warp tension, a number of times. There never seems to be enough said about the tension of warps, when bead looming. It is actually one of the most troublesome parts for a beginner loom artist. The type of loom has much to do with warping and keeping good tension, but once the large part of your looming is complete, tension troubles can creep up again.
In the picture below, a close up shot of one recent looming still on my loom, you'll notice the curving of rows of loomed beads, more to the left in the photo. This occurs even though you feel your original tension of the warps were perfect.
The reason is because each row of beads you add, pulling the weft taut, also pulls the outside warps into the end bead hole. Thus causing the outside warps to shrink in length. This very fact is also why the 'continuous' warp style loom creates such a problem. The outside warps will pull inward, or shrink even more. Because each warp was wrapped continuously around the upper and lower warp bars, the increased tension of the outer warps progressively pulls from the tension of the inner warps. Thus creating the center warps to relax to the point of not having control, or looping.
Another reason warp tension gets uncontrollable is during the time you are edging your piece, on the loom. That too can make the outside warps shrink inside of bead holes. There are some that like to edge 'off loom', but I am one who likes to edge 'on loom'. I love the way my piece is being held, as opposed to having it flop round the table and my thread getting tangled in the edging already completed.
Consider using a loom which allows for each or every other warp to be secured prior to the next warp being added. I have even double wrapped my warps, before continuing to thread the next warp.
Another good feature of a loom to consider is tension adjustments. There are many looms offering this feature. The Mirrix brand looms are very well known for this, as well as any loom that will have hardware adjusting rollers or collapsing ends. You won't need to worry about the adjusting of the warps, once they are wrapped as I discussed above, but when you reach further down your looming, as I show in the picture above, it is nice to release the slightest bit of tension to relax what I have already loomed. Being able to do this, keeps your looming straight and square. It also will not 'pucker' when cut from the loom.
All in all, just consider how you are warping the loom, when you start. Keep the tension relaxed, secure each wrap of the warp, keep in mind each weft pull also affects the warp tension and if you can relax the tension on the loom as you move along, then try it.