Making ribbon browbands is a really fun way to spend an afternoon.
Your horse may have to put up with your first few embarassing attempts, but you can get the hang of it pretty quickly.
These instructions are for the checker pattern on a 1" wide browband. You'll need thinner ribbon for a 3/4" band.

A Browband: Either PVC or leather. Measure an existing band from outside loop to loop.
Satin Ribbons: I use double-sided satin. It's smoother, doesn't wrinkle as easily and gives a better quality finish.
Glue: Don't use basic craft glue or hot glue guns if you can avoid them. They're not strong enough and your browband will fall apart sooner rather than later. Test your glue first to make sure that it does not stain through the satin ribbon.

You'll need four lengths of 7mm wide ribbon.
Your first main colour should be 3metres long. I generally pick the dark colour to be the long one as it'll go around the back of the band and won't look as dirty as lighter colours.
Pick three other colours for the three horizontal rows. I've used one colour twice for the top and bottom row. Cut them a bit longer than the length of your band.

Glue the ends of your three short ribbons horizontally to the start of the band. Then glue your fourth ribbon down across all three of them.

Lift the top and bottom row ribbons up and leave the middle row laying flat against the band. Wrap the long ribbon around the back or the browband, and lay it down as a new 'column'. It'll go under the two rows that have been lifted, and lay ontop of your middle row.

Then lay the top and bottom rows flat against the browband and lift the middle row. Wrap the long colour ribbon back around the browband, creating your next 'column'.

Again, lay your middle row back against the band and lift your top and bottom rows. Wrap the main long ribbon back around the browband and create a new 'column'.
Try to keep the ribbons taught, and continue doing this until you get to the loop on the other end of the browband, then stick all the ends down.

When you're done it should look something like this.
I've added another ribbon to the middle row. There are heaps of different things you can do to glam it up a bit more, and there are loads of different colour combinations you could try.

Unfortunately that's the easy part.
Rosette designs, flag designs, what to use as a base and the sturdiest way to attach them all the to band have proven to be the most difficult part (for me).
You can create the rosettes by glueing the ribbons onto cardboard, but they probably won't last very long. I'll go into rosettes at a later date.

Please let me know if this guide has been helpful -