The increase in yield only REALLY applies to situations where your either growing outdoors, or you have enough space indoors to turn a plant into a TREE rather than a plant. It increases the number of budsites on your plant, yes, but it doesnt nessecarily increase your yield, as your sacrificing the giant showcase nugget that would have grown out of the one top rather than two or four smaller nugs growing out of multiple tops.
The main reason people choose to top their plants, is to keep their plants short and bushy, due to height restrictions in their growing area.its an excellent method to use if your in a situation like that, and i would highly recommend it if you dont have much room to grow.
I personally have topped all of my plants since i started growing, but this time around i didnt need to, because i had more than enough height to grow six to eight indicas out to their full potential, and im actually regretting the descision at this time -- my plants could have been 3-4 feet tall, but since i topped them twice, theyre only around 18 inches, and will probably only get to around 2 feet by the time they are ready to be chopped (1 week into flowering right now). I started up some White Widow Sativas a little more than a week ago, and im not topping them, as i am interested in seeing how an untopped plant grows out.
Basically what you do when you top a plant, is Wait until the plant grows out about 3-4-or 5 nodes (sets of alternating branches), and then you snip the main stem, right around the 2nd node, at the intersection of branches, where you can see two tiny tufts of new growth on either side of the main stem. Once you do this, the main stem will stop growing out. The two tufts that look like almost nothing, will then take over the main growth in height, and turn into the new main branches. Theyll grow nice and thick, although not as thick as the main stem, but they will be big enough to grow out some nice sized main nuggets. You can top really as many times as you like, but most people only recommend that you top up to 4 times, as you can get to a certain point where you start stressing your plant out, and could end up with hermies, should you top too much. Each time you top a main stem, two stems grow out to replace it, and thats why so many people like to do it, because it means more buds, but it doesnt nessecarily mean more weight by any means.
Its possible that in some cases if you take it too far, or you top at the wrong spot, that you could hurt the growth of the plant, to the point where you actually decrease yield, and possibly potency of your bud in the long run...
either way, if you have height restrictions, or space restrictions in general, i recommend topping your plant once or twice, doing it that little wont really hurt the plant at all, as long as you do it right. There are pics all over RIU of plants that have been topped, and in the FAQ there are instructions on how to do it properly.
good luck, and i hope your grow is successful bro.
K1.
*edit* the answers given in the FAQs are not standardized answers by any means. They have been written out by our host Rollitup, and a bunch of other expert and master growers, who know their shit. The methods that they give you in alot of cases may not be the only way to do something, but they are by far the best method. In some other cases, there are other ways to do things that could prove more effective for you personally, but as far a Topping goes in particular, thats pretty much the only way to do it. its just one simple snip, n thats it. There are no cookie cutter answers here man.