I recently appeared for the Salesforce Platform Developer I certification and I am happy to have cleared it in one Go! This has also given me the confidence and base to get ready for the next ones.
Since many people have already written a lot about this topic, I would quickly share my 2 cents on how I prepared for it and what I recommend.
First of all, I hope you have minimum 6 months of experience working with Salesforce as a developer. This is so that you understand basic terminology. Also, you should give yourself the time to get to know the system.
There is nothing more disheartening than to see a developer who is "certified" and doesn't know the basics.
- Start here. Snehal has written a very detailed guide topic by topic. There are embedded links to documentation which a big plus.
- Trailhead is the BOMB!! Hopefully, you have already signed up and have a Trailhead account. Check out the Developer Basic and Intermediate trails. They are very helpful. Apart from that they work as a good summary / refresher about any topic to give you confidence.
- Keep taking notes. I wrote 5-7 word sentences to keep it short and crisp. Then go through them on my way to work or when I found time.
- Read developer documentation for sections that you think are your weak areas. This helped me understand the concepts in a much better way.
- If you can afford a small fee of $19, sign up here and give the mock test. I kept giving a test every 1-2 days until I was hitting 80% plus regularly.
Hope this quick guide helps you in your quest. If there is something I missed or you want me to add to this, please leave a comment below.