Hi I use the pen tool in isolating a part I want from an image and someone told me it's easier to do it with channels. I tried looking for tutorials online and so far have been unsuccessful.

Any ideas?

First of all are you using PS and if so which version? What you are looking for in PS is called Masking.There are different ways to do it depending on older or newer versions of PS. Here is a link to assorted tutorials on just the topic of Masking!
http://www.google.com/search?hl=en&q=masking+using+channels+in+photoshop&btnG=Google+Search&aq=f&oq=

Now the real question comes up, How much PS experience do you have and how much of the program tools do you actually know? There are different techniques or chopping (taking pieces from other works.) Now with masking in the newer versions of PS 2 and 3 there is a technique for layer masking that is pretty simple. Using the gray and white icon in the bottom of the layers box next to the fx. It will make a mask appear beside your selected layer and then you start painting the image with black to cover parts and white to uncover them. Hope this helps you will get more info from others I'm sure.

I am a Pen Tool man I hardly ever use channels unless it is to rob the highlights off of something, but you have come to the right place. A Photoshop Guru will be by shortly to help you they always do.

If you ask it they will come

I have a e-book on channel masking. Learned a bit from it. It's been my experience that channels are good for masking out things with complicated or soft edges (especially hair) while the pen tool is best for objects with defined or simple edges.

not the one I was looking for...but seems to explain it clearly enough.
http://www.markcelagraphics.com/tutorials/zebra_tutorial/channel_masking_tutorial.htm

found it...
http://www.photoshopsupport.com/tutorials/colin/masking-images.html

Making a selection using channels can be done, but that's more something you do when you want to isolate a sky, or background, depending on the contrasts between them.
For example, if you have a man standing against a background (let's say a sky and some trees and you want to isolate the sky), then you go to a channel, you see which channel has the highest contrast (usually blue) and you duplicate that channel.
In the duplicated channel, you press CTRL+M to open up the Curves (command+M on the Mac) and you set with your colourpicker in the curves-menu your black point and white point and use the curves itself to get a even higher contrast.
Once you did that, you select the white or black part of your image (eventually use the lasso-tool to add/remove parts in your image), remove the duplicated channel again to go back to RGB and back to Layers and there you have a selection of the parts you wanted or didn't wanted to keep.

Hope that helps

cut and paste/ ask marco

Try this book. It's a good'n.
http://www.amazon.com/Photoshop-Masking-Compositing-VOICES-Eismann/dp/0735712794/ref=pd_bbs_4?ie=UTF8&s=books&qid=1220824254&sr=8-4

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Easy does it

If you are using Photoshop there are a lot of ways to isolate part of an image: layer mask, channel mask, lasso tools, pen tool, magic wand, selective color, background eraser, etc….. the specifics of the photo will determine which is the best one to use. If a photo has decent contrast between the objects in it, then you can use a channel mask. If it has fine detail like hair, and has good contrast, then using a channel mask can do the best job while saving you a lot of time and work. The other good thing about channel mask is that you are not changing the original photo, and you can go back at anytime to make more changes.

To use channels to isolate part of image:
• Choose a layer to work with
• Open channels palette
• Click through the red-green-blue channels to see which gives the best contrast
• Duplicate best contrast channel
• The object you want to isolate needs to be in complete contrast (black or white) to the rest of the channel:
1 - Open levels (pc: ctrl-l) slide the black & white input sliders towards the center to increase contrast without destroying edge detail. You can repeat this if needed.
2 - Use black and white brushes to complete mask
• In masks ‘black hides’ while ‘white reveals’ – so if the object you want is black invert it (ctrl-i)
• Load the duplicate channel you made
• Click the rgb channel (or ctrl ~), you will now see the mask selection
• Create ‘new layer via copy’ (ctrl-j)

You have now created a new layer with your selection in it. You can go back anytime and adjust the channel mask to create a new adjusted layer (just make sure that the original layer used for channel mask has not changed).

There are some other good things that you can do with channels - if you want to learn more about channels I recommend reading 'The Photoshop Channels Book' by Scott Kelby.

Hope it helps, JW