I've had a similar problem, which may be different to your problem because all the computers in my house share the same backup drive, and so there are lots of different backup files.
My problem (which I fixed) was that Migration Assistant couldn't see the backup drive, but it turned out that if I opened the drive in Finder, and then opened the '.sparsebundle' file that belonged to my computer, then all of a sudden the backup drive became visible to Migration Assistant and I could restore from backup.
Besides the obvious issue of you having too much information to load onto the SSD, I've done this basic procedure in the past. However, it's much easier now using Time Machine, but you have a few options:
Time Machine
If you don't currently have a backup that can hold all your data, do yourself a favor and pick up a drive that can. Time Machine should be built into the OS you're currently running.
Do the backup. For 400 GB, you probably want to set it up before you go to sleep and let it run overnight. Once it's complete, unmount the drive and unplug it from the computer. Go through with the drive install and then install Lion. When the computer reboots, before you start to work with the setup assistant, plug in the new drive. At some point it will prompt you for a location from which to migrate data. Select your backup. Let it run for a while and when you get back, it will contain all the data you backed up, in a usable form. This is my current favorite method for cloning user workstations.
Super Duper
If you can't get an external backup, you can use SuperDuper to create a full-system backup from the active system disk. You'll have the ability to trim the data to the size of the disk to which you're copying in the interface. This route is a little more technical and requires a bit more time hands-on.
File Copy
I wouldn't recommend copying a user folder for a logged-in user due to open preferences files. You'll get all kinds of "File In Use" errors and it will probably exit the copy prematurely. Instead (if you're dead-set on using this method - which I advise against) create a second admin user and copy the folder over into a temporary location before staging it into the actual /Users/ location. You'll also need to make sure the permissions for the entire folder are set so that the user whose home you are copying can actually access and write to their files. To do this, you can use the Finder's Get Info on the folder and then add the user to have full permissions. Once it's staged into the /Users/ folder, you can log back in to the main user and delete the secondary admin. You may have permissions issues in the future using this method.
All that said, it's totally worth it to get an external to back up to for Time Machine to clone your new SSD from.
Best Answer
You'll need to copy two files from the old installation of OSX:
The first tells Dashboard which Widgets to show, the second contains your notes.
Copy these to your new
~/Library/Preferencesand you should be good.You'll need to restart, logout and login, or kill the Dock, for example by opening Terminal and running
killall Dock.It worked for me - but I should warn that my home path was the same on the old install and new install.