A few things i picked up
it takes 7 shots to create a new virus, also the distance covered is barely 10boxes
the new virus moves according to YOUR current movement direction(not the direction of the shot)
turn on numbers in options
you can start to "W" when you're size 32, you loose 16size per "W"
Most virus' are size 100(starter) and get increased in size when being fed "W"
usually i feed a virus to almost exploding (6x) i get myself to 150size and just hide inside the virus, some guy will usually pass through thinking it's ok and i'll consume him. (don't be too big, you might actually eat then explode)
If you're top dog or top3, i usually find a corner to put myself in, that way i can then just box in a guy that decides to run along the edges.
Also using the edges is a great way make yourself whole if you've split too much. find a corner spam "W" into the corner and just reabsorb yourself to become 1 whole big blob again. You loose mass doing this, for every "W" you shoot, you loose 2mass on absorbtion.
If you find that too tiresome put your cursor in between your 2 or more cells, that way your trying to force them into each other. Note you can only do this 30s after your split.
Note, for some reason, ppl are dumb enough to follow a trail you leave behind, if you "W" to lure a guy into you, it works!
Being top dog is boring most of the time, you just sit there loosing bubbles, and you're so big and fat, it takes forever to get anywhere. But you have to eat to maintain your top dog status, usually i just camp a corner and ppl come into you after a while.