Where do you turn when you want to use a diagram to show a sequence relationship or a relationship between entities (two of the six categories of messages I overview in this SlideShare deck)? Microsoft will tell you to use SmartArt. I suggest you don't use SmartArt. It is inflexible, hard to edit, hard to customize, hard to animate, and not easy to select a diagram that communicates your message.
Instead, I suggest you go to Diagrammer.com. This is a part of the Duarte.com site by the presentation experts at Duarte Design in California. I consider Duarte to be one of the top high-end presentation design studios in the world. Here is the step-by-step process to select, download, and edit a diagram from this collection.
Step 1: Select the category
Start at Diagrammer.com and select from one of the 14 categories of relationships shown. Read the description under the title to make sure you are selecting the right category.
Step 2: Select the number of objects and 2D/3D
Within the category, you select the number of objects you need and then whether you want 2D or 3D (please always select 2D). Note that the way the system works is that you are shown the same images to select the number of objects regardless of the category of diagram you selected. Don't be concerned that the images you see of one node, two nodes, etc. don't match your diagram category. Just select the number of objects you need in your diagram.
Step 3: Select the diagram
Now you are shown all the diagrams that match the criteria you chose. There can be more than one page, so make sure to go to the other pages if the link is shown at the bottom of the list.
Step 4: Download the file
Once you click on the diagram you want, you will be asked to enter your email address, position, and company name (all are required fields). Once you submit that information, your file starts downloading. Save it to your computer so you can work with it.
What you download is a PowerPoint file that contains the diagram on the single slide in the file. Each of the objects is separate on the slide, so they are easy to edit.
Step 5: Edit the diagram
Many of the shading effects are created by grouping two objects into one. The shading on the arrows above is done this way. When you click on the object, it appears that it has no fill color, but that is referring to the grouped object. Once you ungroup the shapes, you can see and set the fill colors. Regroup the shapes if you want to still have the shading effect.
If the overall size of the diagram is too big, the best way to resize it is to first group the drawing objects in the diagram (the arrows and the center box above). You don't need to include the text boxes or leader lines. Then resize the group by holding the Shift key down and using one of the corner sizing handles. This resizes the objects proportionally. Ungroup the objects once you have them the right size.
Because each object is separate, you can move them, change their color, and add or remove text. This gives you a lot of flexibility to create the exact diagram you need. Because the objects are separate, it also makes it easy to animate the pieces of the diagram to appear one at a time as you explain each piece.
For situations where you are showing a relationship of flow, sequence, or between entities, Diagrammer.com gives you access to thousands of customizable pre-made diagrams you can use right away.