Learn how to write like monks of old or the name lettering of your favourite newspaper! All you need is a wide-nib pen, a steady hand, and patience.
Step 1: Find a Reference Alphabet
You'll need a reference for your Gothic lettering, so just find something quick on Google images. With practice you'll come to remember them. You shouldn't adhere too rigidly to it though; calligraphy is an art, and like any art you're free to scribble around and get creative! More on this later.
Step 2: Using Your Pen
Hold your pen at about a 40 degree angle from the horizontal, and keep it at that angle. Gothic lettering has a more consistent format than most, making it look more uniform than others. Gothic calligraphy was invented to be written densely, so that means no wasted space. You also don't want your pen to dig into the paper, especially when it's soaked with ink, so always make your strokes down or to the right. Keep an eye on the reference as you make each stroke. You'll find that getting consistent lettering is surprisingly easy!
Step 3: Try Easy Letters
Gothic lettering is about as ornate as it gets, so pick a couple with fewer strokes, allowing you to get used to the style. Try to plan your strokes before diving in. Ideally, especially with complicated capitals, work outside-in; this will allow you to frame your letter and fit it easily in a line of text.
Step 4: Dive In!
You can practice writing each letter again and again like in kindergarten, but I would recommend just diving in. Gothic letters don't exist in isolation, they're consistent in style. Practicing one means practicing all of them!
Step 5: Make It Your Own
The only consistent feature of Gothic calligraphy over the centuries is that everyone made it their own! The reference is only your starting point. Try just scribbling and making things up, especially on the capitals. You can come up with some ornate and beautiful designs!