There are many great posts out there on traits of a good Product Manager - understanding the customer, being the voice of engineering and design, etc. However, I have seen fewer posts on how to be an effective Product Manager.
The below ways are based on my experience as a Product Manager at Facebook and LinkedIn, but are useful for Product people in companies of ALL sizes - including startups.
Learn the org map
The first thing you should do on your first day is learn the org map. Learn who runs each organization - product, eng, design - for all product groups, especially the important ones or the ones you will interact with. For instance, if you’re at Facebook, you should make sure you know who’s in charge of News Feed and Profile - as those are going to be key drivers of traffic to your product.
Meet with everyone
You actually don’t need to meet with everyone, but as many people as you can - especially the ones in the important roles you have identified above. Have lunch or coffee with them, grab a beer after work, get to know them. As a Product Manager, especially in a big org - or even as an entrepreneur looking to gain traffic for your product - relationships are crucial to making your products successful.
Learn how to say no
One of the most important things a Product Manager must do is learn to say no. There are limitless ideas from everyone on your team. And often, there are every more ideas from other teams looking to integrate with you - especially if you are working on a core product.
First, you need to identify which ideas are good and which aren’t. And then, even for the good ideas, you have to prioritize - there is no way you will be able to do all of them!
However, in both cases, you have to learn to say no gracefully. It is important not to anger others - either people on your team or others. You will need their help to ship product now or at some point in the future. So either way, learn to be gracious in your no - say why it is not the right idea now; otherwise, you risk losing their necessary support when you will most need it.
Don’t hold grudges
Finally, if someone makes a decision you don’t like - especially one that affects you - do NOT hold a grudge. This may be extremely hard to do sometimes; however, you never know when you will need someone’s help.
So while it may be hard to do so, make sure to never hold a grudge. Instead, make sure relationships with your coworkers - especially leads on the key teams you need to make your product successful - are as good as possible. And this not only goes for Product Managers, but for entrepreneurs as well. The Valley is a small place - and people are more willing to go out of their way to help people they like.
These are the ways I have found to be an effective Product Manager. If you have others, definitely send them over!