Use seedless cucumbers and grape or cherry tomatoes, since they are not as watery as seeded cucumbers and whole tomatoes. If you do use latter, use a spoon to remove the seeds from the cucumbers before slicing and remove the seeds from the whole tomatoes. Grape/cherry tomatoes shouldn't be a problem, but if they are very juicy, drain them over a fine mesh sieve after slicing before adding them to the salad. For best results, chop everything in advance, but toss it with the dressing right before serving, so everything is as crunchy and not as watery as possible.