Consistency - The jelqing grip should be consistent throughout the stroke as proper consistency ensures proportionate growth. It is easy to subconsciously increase or rotate the grip part way through a stroke.
Starting at the base - Your grip should be attached as low down on the shaft of your penis as possible.
There are two ways of applying a standard grip to you the penis: palms up (a normal OK) and palms down (an overhand OK). It is not required for the forefinger and thumb to meet (OK grip), you have to fit yourself and make the blood circulate efficiently. So, it is up to you to decide whether you apply an OK grip (with the forefinger and the thumb met at the end) or U grip (with the forefinger and the thumb not met). Proceed with what works best. A U grip applied vertically will tend to work the corpora cavernosa (CC) most, increasing the girth of your penis.
If you have no curvature or bend or have no attention to correct it, apply the grip straight. If you want to correct a slight curvature, then apply the hold diagonally and place the leading edge of the grip on the inside of the curvature. Remember the process is long-lasting and slow and no dramatic correction can be reached.
Jelqing is a combination of stretching and internal pressure. If you apply stretching and length, it less effectively traps blood but is deemed to be stronger and sensible. You have to rotate the grip at the point of application. Also, if the first grip becomes a short stretch at the glans while the second grip is applied this is likely to have positive length effects.
The penis has a lot of sensitive nerves that can be damaged during jelqing. So, you must remember them and avoid any injury. The dorsal nerve runs along the top of the penis. You make your best not to cause any harm to it. There is also a particularly sensitive nerve bundle just below the glans. Do not press on by terminating the stroke an inch before the glans or avoiding the bundle with a grip biased to sideways pressure.
An overhand OK seems to cause less harm to the nerves of the penis as the webbing is between your thumb and forefinger. By applying an overhand OK, you can safely continue stroking to the glans with no termination.
It is highly advised to change the grips applying overhand and standard OK by turns, and rotation of the grip at the point of the application during the session. It ensures that the entire penis is involved in the procedure and trained.
The perfect warm wrap is a good beginning. And when you start with a low-intensity grip and increase the intensity during the first minute or so, it can help avoid spotting.