Now we come to the point of explaining the main purpose behind growing Tulasi. That purpose is to have Tulasi leaves and manjaris to offer to Krishna. Krishna is very happy when we offer to Him Tulasi, especially manjaris. It is said that Lord Jagannatha does not accept any of his offerings without Tulasi, and that by offering a manjari to Krishna one gets the same credit as offering thousands of every other type of flower. So, we must know the proper way of going about collecting Tulasi leaves and manjaris.
Collecting leaves is quite easy. All you have to do is hold onto the leaf you want to pick with your right thumb on the top of the leaf and index finger on the bottom of the leaf while keeping the branch steady with your left hand, and gently pull downwards perpendicular to the surface of the leaf (in other words, if the leaf is at an angle, pull downwards at that same angle). With very little force the leaf should cleanly come off at the joint between the stem and the branch. The best leafs to pick are the bigger, older leafs, rather than small new leafs. It is also best to pick leafs from a variety of branches, so that you don't end up with a branch that is completely bare.
When it comes to picking manjaris, it gets a little more difficult. You have to be able to judge at what maturity to pick them, at what maturity it is too late to pick them, and where to pick them. However, once you get the hang of it it is also relatively easy.
The first step is finding a manjari. These can be found at the ends of branches, and look like the picture below at the young stage. As they grow more mature, they will get longer, and the different sections of the manjari which hold the flower buds will become more and more separated, as shown in the second photo. Then, flowers will bloom from the buds, like in the third photo. At this point, the manjari should be picked.
So the next step is knowing where to pick them. If you look at the first photo, you can clearly see two green things at the base of either side of the manjari where the leafs meet the stem. At the next set of alternate leaves are two more green things, etc. These green things are either manjaris or new branches growing. If they are manjaris, then it should be clipped below that set of leaves. However, if at the next set of leaves are two more manjaris growing, then the clipping should be done below those leaves, etc. The first set of leaves on the manjari will always have two manjaris growing. Sometimes, and on some plants it is more common than others, the next set of leaves will have two more manjaris, and even the third set of leaves may have manjaris. So one has to be mindful of where to clip. The manjaris will look compact and cone-shaped, just like the top of the main manjari. If branches are growing, it will look like two leaves growing on each side of the stem.
Sometimes the first set will look like branches rather than manjaris, like in the second and third photos. This is, however, just a "trick"- it will without a doubt be manjaris.
Here below you can see an example of the "trick" I mentioned. Just below the manjari are two sets of leaves, which is exactly how it looks when branches are going to grow there, and thus normally you would not want to cut below that. However, since it is the first set of leaves below the manjari, we know that where those two sets of leaves are will actually be manjaris.