I find cucumber to be pretty bulletproof Ashley. If a few leaves get chewed who cares. If the
plants are healthy, they are such prolific growers it would take a plague to slow them down. Ensure plenty of potassium is available to the
plants and they will laugh at most pest problems.
For tomatoes, my biggest summer problem is fruitfly on semi ripe fruit. I use a mosquito net over the
plants once the fruit has set. I went to an open garden last weekend where an old couple were using discarded lace curtains, sewn together, to protect ripening fruit on tropical fruit
trees.
As Duckie suggested, be specific with your problems. The methods of overcoming them are likely to be many and varied.