What follows assumes that Lightroom 3 has more or less the same controls as Lightroom 4/5 which is what I use.
In Lightroom 4 in the develop module in the Basic panel on the right you will see Black and White. Click on this and it will remove the colour. You can now use the sliders to adjust the image to what you want. On the left hand side, under presets you will see some black and white presets, high contrast, low contrast etc. These can be a good starting point for adjustment in the basic panel. Once you have made the initial conversion you can 'adjust to taste' with the sliders.
In the HSL/Colour/Black and White panel select black and white This allows you to adjust the tones of various colours within the black and white image which gives you more control over the adjustments.
There is a very good Lightroom plug-in, 'Silver efex' which gives you more options but lightroom on it's own does a pretty good job.
Much better to shoot in colour and then convert using good software because it allows you access to the ful tonal range of the colours in the image. The only alternative to this would be to buy a Leica Monochrom.