In really simple terms, you will struggle to obtain accurate colour when relying on a software utility. Hardware calibration with something like an i1Display Pro is absolutely the right way to go, because it can accurately read the results from your display and create a profile to correct for errors. Unless your display is properly calibrated it's all just a guessing game.
Displays change over time as they age, but hardware calibration will keep the display looking consistent if you run through the process once a month on average. Another advantage is that your display will be calibrated to industry standards practiced by photo labs etc, so you are all looking at more or less the same thing as well. What you see on screen is what you should obtain in print.
Thanks for the response, I will take a look at your book. I also want to make sure that the printer I am using prints consistent with what I see on my iMac after it is calibrated.
1. After bringing a photo into Photoshop, do I just simply choose edit > assign profile and select the printer profile to do this?
2. Do I need to do anything with the edit>color settings or edit>convert to profile?
Let's take one step at time, but I'll explain it in really simple terms. First you have your display profile which controls your display. Everything that follows should essentially match what you see on screen. This is why it's essential to use hardware calibration.
When you open an image in Photoshop, it should already have an embedded colour space, such as sRGB or Adobe RGB. The point about these colour spaces is that they are device independent, so if you send over a file in sRGB for example, Photoshop will know exactly how to render everything and I'll have access to the exact same information and file data as you. Assuming we both have calibrated displays the image should look very close indeed.
When you come to print, your document profile will be that RGB colour space and you should keep it that way. The change comes where you apply the printer profile, which is device specific for your combination of printer, paper and ink. This is something you can apply in the Photoshop Print Settings and then turn off all colour management in the printer, though thankfully this happens automatically nowadays on Macs.
Assuming you have a calibrated display and a decent printer profile your results should generally be excellent every time.
Modern displays are definitely less prone to drift than the old CRT types, but that consistency becomes less stable over time as the display comes closer to the useful end of it's life.
Hardware calibration is an excellent way to assess the overall condition of your display as it ages, because you'll have no problems hitting your luminance targets when brand new, but over time that will become progressively harder to achieve. Obviously a lot depends on active usage, so if you only have the computer on for a couple hours a day it should last a long time, but if you have it switched on all day you may be surprised how quickly it shows problems. This is particularly evident with budget priced displays.
If you calibrate once a month, chances are you won't see much difference, but if you leave it 6 months the difference is likely to be very evident. In some colour critical environments like prepress or photo labs it wouldn't be unusual to calibrate once a week.