Hi, welcome to the forum. We are just getting started.
I actually taught myself objective-c after only writing c# and c++ for years. I actually read a book by
Jonathan Zdziarski (one of the first people to hack iPhone) that had a great overview of how to do basic things in objective-c that was easy for anyone that knew another c language to understand. I also read through a lot of sample code after that and was able to pick up on it fairly quickly.
I would say find a good book on the subject and collect as much code as you can from the internet and read through it.
You might want to get a MacOS/Cocoa specific book, but if you are interested in the book I mentioned above you can find it on Amazon here:
Amazon.com: iPhone Open Application Development: Write Native Objective-C Applications for the iPhone: Jonathan Zdziarski: Books