Today I has my first session removing suckers from my tomato plants .. all 40 of them.
It's really a job that should be left to an expert (that's what I tell my wife when I try to encourage her to do it). I had my knee replaced recently and at this stage I am no good on my knees.
Before I start removing the suckers I always remove the lower side shoots so as to gain a clear view of the main stem. This helps with ventilation and also allows you a space under the tomato plant to grow a 'catch crop' ... somewhere for lettuce, peppers or radish etc.
As a rule I still remove the suckers when flowers are present and when the plants are around 4' tall, I nip out the growing tip and leave the top two or three suckers alone. Fruit will still grow from these, but it will be up in the air and clear of the ground. Remember when the lower shoots have fruit on them they will be dragged down because of the weight.
Just keep removing the suckers as the plant develops .. you are doing yourself a favour by directing the growth to the fruit rather than into side shoots ... more and better fruit !