David's suggestion is a good one.

Here in my shop we do exactly what he suggests. We take the customers fabric and pin it up three, four or ten different ways.
We then shoot pics and send them to the customer to choose from.

Here is a set of pleating samples for the Isle of Skye Tartan.






If you have a large piece of glass laying around drop that on top of your samples if you wish.

And here is a pleating sample of our own X Marks Tartan.



If you already have the fabric it would be a matter of a few minutes playing around with your fabric to 'get to know' your Tartan. Looking at it this way helps a lot when you get ready to start pleating and stitching as you become real familiar with the elements of the Tartan you are working with.

A note: when laying out your pleating samples make sure you look at how each pleat will be tapered. If you layout with one stripe or element right along one edge of a pleat that stripe may disappear when you taper changing the entire look you spent all that time working on.