Start with a few rows of plain basic tabby before doing anything fancy. Hold your loom upside down to make it easier to scrunch rows down against the top of your loom or against the paper spacer.
If you used a paper spacer, your first weft string should go the opposite way of the paper.
Tips to make following your cartoon (design) easier.
You can transfer lines directly onto your warp stings or loom.
You can slide your cartoon behind your warp strings so you can look at it while you weave and try to line sections up.
You can create paper spacers to block section out.
You can keep your cartoon handy and mark areas off once you have added them.