@msnancy - The key ingredient for capturing sharp subjects against buttery smooth backgrounds (bokeh) is to use an aperture between f/1.4 to f/2.8.
Your 18-135mm lens can only go down to f/3.5 when shooting towards the wide-end (18mm) and f/5.6 when shooting towards the long-end (135mm), so you'll want to use your 50mm lens which can get down to...you guessed it...f/1.4. :)
In regards to settings, you'll want the ability to control aperture and let the 60D do the rest for you. To do this, just enable Aperture priority (Av on the mode dial) and use the smaller command dial (near the shutter) to select the lowest available f-number...which in this case will be f/1.4. In addition to that, I would also set your ISO to Auto to ensure you get accurate exposures.
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Your 18-135mm lens can only go down to f/3.5 when shooting towards the wide-end (18mm) and f/5.6 when shooting towards the long-end (135mm), so you'll want to use your 50mm lens which can get down to...you guessed it...f/1.4. :)
In regards to settings, you'll want the ability to control aperture and let the 60D do the rest for you. To do this, just enable Aperture priority (Av on the mode dial) and use the smaller command dial (near the shutter) to select the lowest available f-number...which in this case will be f/1.4. In addition to that, I would also set your ISO to Auto to ensure you get accurate exposures.
Hope that helps and happy shooting! :)