Properly spacing paragraphs? By that, do you mean you have trouble deciding when to end a paragraph and when to start a new one? Or...literally spacing a paragraph? xD If it's the former, then there are many ways to determine paragraphs in the world of fiction.
Usually, though, you treat paragraphs like you treat sentences; each paragraph generally contains a unique frequency. For example, in a situation containing a conflict of action or of thought, each paragraph can demonstrate a shift of action, or represent friction to a prior thought. Think of it as giving the reader a moment to catch his or her breath. Or a pause in conversation. After such a pause, the mind is fresh and ready to tackle a new idea...and thus begins the next paragraph.
But really, when it comes to structure, you should do whatever you think will help tell your story better. If the pace is fast, try to keep your paragraphs short. If things are slow, or if you're in an expository phase and need a lot of detail, then you can take more liberties with the lengths of your paragraphs. In fiction, there may not be a solid "right" way of using paragraphs, but there are "efficient" ways. Just read it to yourself afterward. If it doesn't seem efficient, then there's probably a better way to write it.
Similarly, there are different ways to use dialogue. I'm supposing you already know about signal phrases (Diana said, "..." Stanley exlaimed, "...!" etc.) But you don't need to use those all the time. Sometimes, if you're describing the character or his/her actions in a paragraph, you can insert dialogue without signal phrases, simply by implying that the speaker is the one highlighted in the paragraph. Be sure you're clear in doing this, though, or you might confuse the reader.
Also, if you have a lot of back-to-back dialogue between two characters, you don't need to signify who is speaking for each and every line. It's almost always necessary to signify the conversing characters at first, but after each succession of lines for each character (assuming you don't have anything other than dialogue mixed in with it all), simply having their lines there is enough. You shouldn't do this too often, though...probably only best used during very fast action - but even then, description can be a better ally.
The main thing of all this, of course, is that whatever structure you choose, it should be for the sake of presenting your story to the reader in the most efficient way. Put yourself in your reader's shoes/socks/bare ticklish feet. How would you think is the best way that you'd become engaged with the story? How well is the story paced? Do you have enough time to take all the words in and analyze it? Is it so slow that you feel yourself becoming bored? Do you know who is speaking simply by common sense, or do you need a hint in the form of a signal phrase?
As the shades of color in a painting helps one visualize the full image, so too should the paragraph structure of a story help a reader understand where you want to take him. Without that structure to help channel your flow of words into efficient canals, it remains a rapid river, unable to conquer.
