Profile does not contain a closed sketch: A profile family has to be a complete loop. If it sure looks like a complete loop, did you copy and paste sketch lines from another profile? Revit fails to acknowledge lines when you do. You'll need to create new linework over the "bad".
I picked the wrong category for my family: Pick the right one, it's not too late. Open your family, choose the Settings menu and then choose Family Categories and Types. Now choose the category you really wanted. Want an interesting trick? Build a non-hosted generic model family and switch it to the door category. You now have a door that won't require a host to place it. This is good for gates in railings.
Stuff doesn't stay put: You need to get friendly with ALIGN and LOCK. Not to mention their friend LOCKED DIMENSIONS. Also be vigilant about the current workplane.
Revit Wants to Delete Types: Several causes...
- Empty Values - You've left a parameter with a value of zero causing geometry to "not exist".
- A Bad Host - The host in the family isn't big enough to host the size of the family you are inserting or... not thick enough.
- A Formula is missing pieces - If you renamed a paramter in the family, Revit deletes the parameter from the formula. You need to recreate the formula entirely. OUCH! (FIXED in 8.1, now it renames the parameter in the formulas too)
- Values Just Don't Work -
There is a value that makes the family break. Most often one value in a family that has several types has a value that is wrong, similar to the Empty Value above.
Unit Conversions go Haywire: Revit insists that formulas are using the same unit types within math operations. So you often have to consider how to convert one unit type to another. There are a couple handy cheat sheets at AUGI. (I'll track them down)
Can't Label my Dimension: You've got a dimension. You've got a parameter. Revit won't let you assign the parameter to the dimension. Most likely you have a value in the parameter that is different than the dimension value. Change the geometry so the dimension matches the parameter value or change the parameter to zero. Revit will let the dimension define the parameter value if it is set to zero.Revit Complains That There Is Nothing To Show in the View: If you create a family that doesn't have solid geometry or Model/Symbolic lines visible in a plan view and you try to put this family in a project you'll get an error telling you that there isn't anything to see. Make sure you put something that is visible in the view you intend to place the object from.
That's enough for now...anything else I should include? Let me know!