Best sequence to follow after, or before, importing pictures using an iMac?

Question

I recently purchased Lightroom 4 to use on my iMac.  I will first be importing several thousand pictures in numerous folders from the iMac finder picture file.  My plan is to organize these numerous folders in a Lightroom catalog, or catalogs; a Lightroom file format which makes sense; a collection set, or sets, and collections.  After I have these pictures organized in Lightroom, I plan to reveiw them, discard, arrange, edit as necessary.  I want the Lightroom file structure in my iMac finder picture file seperate from all the other numerous folders, since I have many more picture folders to move into the finder picture folder from iPhoto.  What do I do first and subsequently to make all this happen?   I will also want to add information in Lightroom about the pictures such as the camera used, when taken, copyright, etc.  And, eventually, I will also be importing new pictures into Lightroom.  Is it best to import directly from a card into Lightroom or onto my iMac hard drive and then into Lightroom?  I assume this will depend first on answers to my earlier questions.  And how do I set up Lightroom 4 so I can migrate between it and Adobe Photoshop Elements 10 which I will also be using for more detailed editing of my pictures?   Any step-by-step directions would be greatly appreciated asap.  Thank you.  

Answer 1

I have a couple of comments
Unless you have a very good reason for using multiple catalogs, you want to go with a single catalog. One catalog. Emphasis on "one". As in: less than two, and greater than zero. I hope this is clear. What would be a very good reason for using multiple catalogs? I can only think of one, and that is if you have photos that have completely non-overlapping subject matter, such as personal vs work, then two catalogs would make sense.
Instead of using "a collection set, or sets, and collections", I would first begin by using keywords as your primary organizing tool. While keywords and collections overlap somewhat, the benefit of keywords are that they can stay with the photo, if that's of interest to you. Thus, if you send the photo via e-mail, or upload to a website, or make use of the photo in other programs, your keywords will be available in all of those situations. If you use collections, these are not available outside of Lightroom. Additionally, you can add captions and other metadata for more detailed descriptions of what is in the photo, these can be very helpful.
"After I have these pictures organized in Lightroom, I plan to reveiw them, discard, arrange, edit as necessary." I would discard the ones you don't want before you do any other organizing.
"I want the Lightroom file structure in my iMac finder picture file seperate from all the other numerous folders, since I have many more picture folders to move into the finder picture folder from iPhoto." Not sure what this means at all, but the emphasis on worrying about file structure (do you mean “folder structure”?), in my very biased opinion, is the wrong emphasis, and will lead you down the wrong path. When you organize in Lightroom, folders are not an organizational tool ... they are simply places to put photos, with no other meaning. And so you can put your photos into default folder names (I use capture date, it takes no effort on my part) and then I use keywords to find all of my photos inside of LR. I never (and I really mean never) use folders to find anything.
"What do I do first and subsequently to make all this happen?" Import the photos. Delete the ones you don't want. Add keywords religiously, and optionally captions and other metadata. Edit.
"I will also want to add information in Lightroom about the pictures such as the camera used, when taken, copyright, etc.  And, eventually, I will also be importing new pictures into Lightroom." Camera used is already present. You don't have to add it. When taken is already present. You don't have to add it. Copyright is something you will want to add, you can use the metadata panel and add it to all imported photos in one action.
"Is it best to import directly from a card into Lightroom or onto my iMac hard drive and then into Lightroom?" It doesn't matter, they are equivalent. Depends on what you want to do. I import directly from the card, as it saves me a step. But either way, the photos wind up on your hard disk somewhere. (For photos that are already on the hard disk, you would import using the "Add" option.)
"...how do I set up Lightroom 4 so I can migrate between it and Adobe Photoshop Elements 10 which I will also be using for more detailed editing of my pictures?" In preferences, you set up PSE10 as an external editor.