Eat more fruit and veg, drink more water, get at least 1 hour of moderate exercise a day, get plenty of sleep, wash regularly, etc.
The fruit and veg will help get rid of toxins in your body, possibly improving your skin.
Drink more water, again, it helps your body filter out toxins and waste products which may not help your skin condition. It also keeps you hydrated, keeping your skin healthier so you're less likely to get dry skin and/or spots. You need at least 2 litres a day, it isn't hard, a pint of water at breakfast, lunch, dinner and in between is a good start. Thirst is a sign of dehydration, you get it after you need water, not before, that is why you should drink regularly, even if you don't necessarily feel like drinking. Yes, if you're getting headaches and your urine is clear, then you're drinking too much, but pale yellow is what you're aiming for.
Exercise warms up your body, opens pores on your skin and helps the skin to clean itself and flush out toxins with the help of sweat.
Don't use too many exfoliators and peelers, yes, they may make your skin feel great and help clean it, but your body only fully turns over your skin every 2 weeks apparently, so anything more regular than once a week can aggravate your skin, making it drier and more prone to infections and spots.
Alcohol and cigarettes are also big problems.
It's about finding a healthy medium between your lifestyle and what you do to your skin. Personally, sometimes my skin gets dry, sometimes greasy, it's about varying your lifestyle to compensate and/or changing skin products.
One of the best ways to get rid of blackheads is to steam your face (with a hot shower, or an intense workout where you're sweating heavily) and then easing them out with your fingernails carefully and/or a blackhead remover.
Sudocream is good at treating spots, don't squeeze or aggravate them, just put some sudocream on and leave them, within a day or so they will have gone down and/or disappeared.
Also it takes about 2 weeks for your changes to show any results, so if it feels like it isn't working continue at it.