Have you ever been reading a book or watching a movie and they suddenly jump backward or forward in time? The general term for this is flashback. If done well, flashbacks can be an effective way to present information that is needed at that point in the story. Done poorly, they can confuse your reader and lose their interest.
To be sure you aren't guilty of confusing your reader, always make a chronological outline that you can follow while writing, even if that is just in your head. Events occur in order so writing about events should occur in the order in which the events occurred.
If you are going to give directions to someone who is driving to your home, you need to know where they are starting from before you know where to begin giving directions. Once that is established, giving directions becomes an easy job.
If they are coming from another city, you need to first get them to your city, then onto a specific set of roads to take to reach your home. The more complex the route, the more you will need to add some reassuring landmarks for them to be comfortable that they are "on course" to their destination.
Conversely, if you are trying to explain to someone who is at your home how to go somewhere else that they have never been before, the same thing applies in reverse.
Expanding this Concept
If I'm going to describe a specific building to you without using any photos or floor plans, and my job in doing this is to have you end up with a clear mental picture of this building, where do I begin to write about it? At the front door.
I will take you by the mental hand and walk inside the front door with you, telling you what I see. I will tell you what's on the right, left, and ahead. Then I will take you in one of those directions and tell you what I see. When I finish with that direction, I will take you back to the front door and proceed in another direction.
I do not begin by telling you all about the grand master bedroom on the third floor, then jump down to the great rec room in the basement because your brain will stop you from listening and ask the question (whether you realize it or not) how did we get into the basement? Missing pieces of information makes readers lost and confused.
Video Camera of the Mind
Think of your words as a video camera that cannot be shut off. Your viewer sees all that you see. When you finish telling them about what you see, they can go back into their mental picture and do what I call "replay the tape" that they made while walking beside you.
If you have done a good job with this, your viewer can repeat back to you how to get from one room to another in a building you described or they can repeat back to you the highlights (in proper time line sequence) of the story you told.
Try this: Describe something familiar such as your home with words. Begin by driving up to the property from let's say two blocks away. What's on the way to it, a park maybe? What kind of a street is it on, a shaded boulevard? What's next door, another house? What's across the street, a quick shop? Try to get the "flavor" of the area surrounding the house. Then get more specific, such as where do you park your car and how do you get from your car into the house?
Once inside, tell your reader what's on the right, left, and ahead. Pick a direction and begin to describe the inside one level at a time. If there is another level to your home, walk them over to the stairs and take them to the next level, repeating the process from the head or base of the stairs.
This exercise, if done properly, will teach you about both time lines (begin at the beginning) and spatial perspective (camera that doesn't shut off). These are two key elements to effective writing.