Choices for migrating your Mac files and settings to a new drive:
1. Boot into Recovery Mode (Command-R) and use Disk Utility to copy the system partition to the new drive connected via an external enclosure.
2. Remove the drive and duplicate using a duplicator.
OR the option I think is best:
3. Install the new drive and reload OSX. Then use Migration Assistant to pull in files and settings from the original drive connected via an external enclosure.
Strategies to make the new drive work well under OSX:
- Use SSD Chameleon to enable TRIM if the new drive is an SSD AND your OSX is 10.6.7 and above. If this software refuses to enable TRIM you need to wipe and reload OSX. If your OSX is 10.10.4 or greater just use the trimforce command built-in to OSX.
- Use SSD Fan Control to quiet the fan if the new drive doesn't support temperature sensor connector
Don't forget to reference the relevant repair guide on ifixit.com so you know how to get to the drive and reassemble things with a minimum of fuss.
Don't forget a 2.5" to 3.5" bracket if you are installing an SSD into a Mac with a desktop hard drive such as the iMac. Avoid brackets that support more than one drive as they might be too large fit in cramped Mac interiors.