<p>Hi!</p><p>I agree with Denny's comment. As a result of the stroke order, I find the lines steeper in ツ/ソ (tsu/so) compared to シ/ン (shi/n), which is a bit flatter. </p><p>In handwriting, some people write with an extra 'hook' at the starting end of the stroke. If you do a google image search for "handwrite tsu japanese" you should see some examples.
</p><p>Also, because katakana is often used for loan words (many English words), you can sometimes guess which character is in the word if you can't differentiate them.</p><p>Hope this helps!