If your plants are directly in the ground you may see limited benefit from liquid nutrients. However, I've had great results with rose bushes outdoors using liquid nutes by waiting until just after the ground has started to dry out after a rain, but not (hopefully) feeding just before one. That gives the plants more of a chance to get to the nutes before they wash away. If the weather holds and the plants need more water, I water sparingly so as to not create a lot of run-off.
Usually though I prefer to use a solid time-release fertilizer for in-ground plants. I've heard good things about Heavy Harvest specifically when it comes to outdoor growing (the browndirtwarrior videos) but I can't say from personal experience.
If you're talking about growing in containers as I'm guessing you are, liquid nutes are great. I would start at quarter strength at the most. Use the calculator on the Advanced Nutrients website and set the reservoir to whatever the amount of water you're going to use. So if you have a gallon jug, set it for a gallon. I would actually recommend having something that holds more than you're making since it's much easier to stir or whatever if you have extra room. Then divide what they say to add by 4, add that amount, stir between each part, and water the plants with it - just enough so a little bit comes out the bottom. Otherwise it's just wasteful.
Next time the plants need water, give them plain pH'd water, same amount. Next time water with nutes, then water without nutes, and so on. If they look hungry give them a little more nutes, if you see the leaf tips turn brown and "burnt" use less nutes.
Pretty simple.
And don't discount the advantage of the tech support line. There's a toll free number on the back of the bottle you can call for help. They've saved my plants more than once.