The beginning of your novel should hook your readers. Keep that in mind. No matter how great the rest of your book is, if people stop reading after the first chapter because it isn't exciting enough, no one will ever know.

The beginning of your book should show two things:

1. What the life of the protagonist is like.

2. The inciting incident that starts building the tension that comes with the main conflict.

Your catchy beginning will either be the prologue or chapter one, it's up to you.

IMPORTANT

Keep in mind that while you are writing your first draft, it is very likely that at some point you realize that you've chosen the wrong starting point for your novel. This is very common. Just keep writing, and finish that first draft. Changing your beginning is something you do in revision.