TODAY'S #SUPtipTuesday by request: How to Paddle Straight! This is also a pretty big issue, and there's more than one way to make the board go straight, but not all are biomechanically sound (i.e. some will hurt if you paddle that way). Remember the YAW of our board (one of the 3 planes of rotation), is controlled mostly by our paddle blade. Yaw is making your board not go straight, but the only way you could eliminate YAW and go COMPLETELY straight would be to somehow magically paddle down the centerline of the board. Impossible.
Technique
So, the best way to get the board going straight is via TECHNIQUE: make sure your paddle shaft is STRAIGHT. Look in the PIC, if you have a photo of you paddling head on and your line is more like line #1 then you won't go straight (my pic above is at a bit of an angle, so please excuse it, I promise you my shaft is straight). Your shaft needs to be in line with line #2, perpendicular to the water. Now, don't go contorting your body and thrusting a hip out of alignment while chicken winging your top arm over your head impinging your nerves atop your shoulders... that would be bad (but all too common). Keep your hips square, shoulders down and back (there should be room for a parrot on your shoulder AT ALL TIMES!), and use THORACIC SPINE ROTATION. If you were a #Fembot from #AustinPowers, then your "guns" would be shooting off to the side of your board (see my fembot arrows in the pic), this will enable you to get the shaft in straight without causing pain and impingements, helping you paddle straight (this is what the pros mean when they say "stack your shoulders)!
Fin
Now, if your T-Spine rotation isn't super awesome yet, that's OK. Grab a bigger fin like the JB Runner or Triangle Cutaway from @FuturesSUP or the "Ray" from Black Project SUP while you practice, these fins have more surface area which is what you want to look for in a better tracking fin.
Here is a great guide about fin selection that we put together at the shop a long while ago: https://carolinapaddle.com/learn/sup-race-fins-choosing-the-right-stand-up-paddleboard-fin/
If you're going to be paddling in flat water, you'll gravitate towards fins like the JB Runner or the Keel which have more surface area concentrated near the board. If its pretty choppy, you're going to want to go with the Triangle Cutaway so that that blob of surface area that is lower down grabs the calmer water keeping you tracking straight AND standing on the board.
Cheater-Cheater Pumpkin Eater
There's ONE MORE WAY to help you paddle straight, but its a "cheat" technically. You want to have good mobility: read "Thoracic Spine Rotation." You want to have good technique: read "good body position that prevents injury." So, you're working on technique (trust me, we all are, and if you're not, then you're a fool!) and you still don't have the Thoracic Spine rotation (here is an Instagram link to a short video with a good exercise for T-Spine rotation https://www.instagram.com/p/BNfUV6ahDPI/?taken-by=aprilzilg) then you're going to get a Hall-Pass to use the "J-Stroke"
Now, the J-Stroke isn't an all-the-time or permanent fix, because it reduces our efficiency. We want to always be efficient. The J-Stroke is used if you need to pull the nose of the board toward the side you're paddling on: i.e. you can't get your paddle blade in on the other side due to a log, rock, or another person's board during a race; you are paddling in a quartering or side-wind and really, really need to paddle on the other side for a few seconds; you need to make a quick adjustment to your board direction when paddling out in the surf zone or catching a downwind bump. We can go into further detail of this magical stroke later, but for now you can practice it to use every couple of strokes to get your board traveling back in a linear fashion without switching sides. Maybe one day I'll do a video all about the J-Stroke. Until then, look it up, its cool.