RadToolTip and RadToolTipManager include several properties to control tooltip behavior:
Use properties Position, RelativeTo, OffsetX, OffsetY to precisely position the tooltip.
Use the ContentScrolling property to customize the availability of scrollbars. Possible values are Auto, None X, Y and Both.
HideEvent = "ManualClose" displays a close button graphic in the tooltip. The tooltip stays open until the user clicks the button.
The Modal property when True grays everything in the background of the tooltip.
The MouseTrailing property when True causes the tooltip to follow the mouse. When False the tooltip stays in the initial position dictated by the RelativeTo property.
The ShowCallout property when True (the default) displays the callout graphic on the tooltip.
Use ShowDelay and AutoCloseDelay to control the timing of tooltip opening and closing.
Use the ShowEvent property to control how a tooltip is triggered.
Use Sticky tooltips to prevent tooltips from hiding when the mouse moves away.
The Title property can contain text displayed at the top of the tooltip.
In addition, RadToolTip uses the TargetControlID property to identify the target element for the tooltip. RadToolTipManager uses the TargetControls collection to identify multiple target elements to "tooltipify".
You can find online demos which set server properties in the Server-side properties section of RadToolTip's demos.