Select multiple categories from front-end

Hi. I’m trying to create a custom front-end form where users can submit their posts. I’m still kinda new to this, but can someone get me started with making a multi-select box for categories? Either with checkboxes (like in the admin section) or with styling the wp_dropdown_categories.

I’ve tried this…

<input type='hidden' name='post_category[]' value='0' />
<label class="selectit"><input value="23" type="checkbox" name="post_category[]" id="in-category-23" checked='checked' /> Dog</label>
<label class="selectit"><input value="23" type="checkbox" name="post_category[]" id="in-category-23" checked='checked' /> Cat</label>
<label class="selectit"><input value="23" type="checkbox" name="post_category[]" id="in-category-23" checked='checked' /> Bird</label>
<input type="submit" value="Submit">

I’ve looked at this but multi-select is not an option.

Any guidance would be appreciated…Thanks!