There are so many ways to answer this but I’ll just summarize each of the following.
Husbandry and genetics- Your never going to get big buds if you do not provide the proper care for your plant. This includes all things your plant requires at all stages of life. Genetics are huge because even if you are a wizard grower, the plant can only do what its genetics allow. So buy yourself seeds from a good vendor that is known to produce giant buds.
Lighting- The most important element to the equation is light and if growing indoors there are so many cheap options on the market that will indeed grow a plant but to really get the maximum out of the plant you need a quality light.
Co2- increase in Co2 in your grow environment will undoubtably produce larger buds than that of a normal Co2 level grow environment. Dr Bruce Bugbee recommends running Co2 if you can from the start of veg all the way through flower. He explains this is one of the biggest impacts you can make to increasing your yields.
I hope this helps.