Visio Connector Tips
The following are a few tips I've learned to make working with connectors in Visio a little smoother. Feel free to contribute your own in the comments.
Set the Line Jump Style to GAP
Visio's default method of depicting connectors which cross but do not intersect is to illustrate one line arcing over the other. This is great for electrical drawings and other schematics, but isn't always accommodating of network topologies, especially when one line intersects a number of other closely-spaced lines.

For a cleaner look, we change the line jump style to "gap," which renders aesthetically pleasing white space to highlight line crossings. From the Developer tab on the ribbon, select Show ShapeSheet > Page. (If you don't have the Developer tab, go to File > Options > Customize Ribbon and enable it.) The page's ShapeSheet pops up in a window consuming the bottom half of the screen. Under the Page Layout heading, double-click the LineJumpStyle key and select "2 - visLOJumpStyleGap" from the available options. Press enter to save the selection.


Turn Off Rerouting
Connectors in Visio tend to be very timid and jumpy: A connector frequently will re-route itself when a shape or another connector moves in next to it. For example, observe how the connector below automatically shifts up and to the left a bit when the router shape at bottom is dragged close to it. This behavior can be quite frustrating when trying to keep connector lines predictable and evenly spaced.

Fortunately, we can disable this behavior. Select one or more connectors, then open the Behavior menu from the Developer ribbon and select the Connector tab. Set the reroute parameter to "Never." The connector(s) will now stay firmly put regardless of how many shapes you place on or around them.

Unfortunately, I have not found a way to automatically apply this to all connectors in a drawing; it must be performed manually once the connector has been drawn.
Change the Default Connector Style
One complaint I have with Visio is that there's no simple way to change the default connector style; for example, to increase the default weight of 1/4 pt to something we can see more clearly. The habit I've held for years is to draw a number of connectors, manually select them all, and adjust the weight of them all at once using the ribbon tools, and repeat as I go. However, there is a convenient way to modify the default connector style using themes.
From the Design tab on the ribbon, select Effects > Create New Theme Effects... and name your new theme something meaningful (e.g. "Thick Connectors"). Select the Connector tab (not the line tab, as regular lines are themed independently of connectors) and the desired weight. Save your new theme and it will be automatically applied to the current drawing.

Now when you draw new connectors, they will be created with the weight you specified in the theme settings. Consider tweaking other parameters of your custom theme as well in order to save time on other common reformatting actions.
Comments
Why speaking always about MS suite.... and don't use Libreoffice....
Regards,
lol dude... there are buttons for that :)
On Visio2007 Go to: View > Toolbars > Layout and Routing
This will give you buttons for both 'never reroute' and 'jump style gaps'
To modify all links just do a 'select all' (ctrl+a) on the visio you are working on and click the buttons you want.. :P
You maybe knew this, but you can select all connectors in a drawing by using 'Select by type' in the dropdown menu next to 'Select' in the Editing section of the Home tab in the Ribbon Bar. Once there click 'Shape role' and check Connectors.
@Riccardo: Because drawings created in open source office suites generally look like ass.
@lolwut: Layout & Routing was removed in Visio 2010 and replaced with the almost useless Re-Layout Page and Connectors buttons. If you find a better way to accomplish what I describe above in Visio 2010 I'm all ears.
Oh man... that is unfortunate..but heh.. msoft always had a way to 'improve' (read 'remove') useful features :))
I haven`t worked with Visio2010 so far so i have no idea :)
That's a great tip! Good that this works in OmniGraffle, too, which I would recommend to everyone on a mac.
And I concur, so far all open source graphing tools I tried sucked.
For the line gap setting in Visio 2010 you can also find it by clicking the Design tab, then the little arrow in the corner of the "Layout" section. This opens the page layout window which includes the option to change the line jump styles for the whole page.
Great article!!!
The one thing I ran into and which brought me to this site was that when I tried to move a shape across a connector, both ends of the connector would become solid red squares and then all hell would break loose. Thanks for the guidance to enable the Developer ribbon since from there I figured out that the default behavior of shapes was to "split" a connector and that is what made the connector not only re-route but reconnect in very strange ways. Once that was disabled I could move my shapes around at will with no fear of a connector getting "flighty" and reconfiguring on its own.
Thanks!!
In Visio 2010, on the ribbon, go to the design tab, then look under the layout section, and click the connectors button. then select the option that says show line jumps.
cheers
Anyone know how to disable connector routing in Visio 2013?
does anyone know how to put text at both end of the connector ?
Another awesome tip ! Thank you very much !
Visio 2010: When working with certain icons (usually people shapes), I'll add a new connector point below the icon's text box. This allows an arrow to connect to the bottom of the shape without running thru the text. Problem is that the arrow tends to make a U-turn thru the text section of the icon. I can manually reroute the arrow, but can't find a way to prevent the U-turn. Anyone else encounter this "feature"? Need to turn it off.


Good tip on disabling rerouting -- this always bugs me. As for default settings on lines and such, there must be some hack to do it, but the theme idea is good too.