1. When things go wrong rethread!
And rethread EVERYTHING, even if you think the bobbin is fine, rethread that too. The jam you had may have pulled the bobbin thread out of it's tension guides, you may not quite have placed the bobbin thread into it's tension guides 100%, for many different reasons, this simple step often solves the issues you have had.
2. Replace your needle OFTEN
If problems persist, replace your needle! The cheapest part of your machine is often the most overlooked part. I have had people arrive for class with the same needle the machine came with after two years of use! Needles wear down, needles bend, and needle wear and tear ALWAYS causes problems. You should change your needle AT LEAST every 8 hours of sewing.
3. Use the correct needle for the job
Think of it like managing in your kitchen with only a bread knife. Each needle type has it's ideal use, and will make a marked difference to your sewing. The right tool always makes the job easier!
Have a look at the helpful needle guide from Schmetz, they even have a handy app available to help you choose the perfect needle for your project!
4. When threading make sure your pressure foot is in the 'up' position
As soon as your machine's presser foot is down, the tension plates are engaged, and closed up, making it impossible to run a thread through to thread correctly. Always remember: Foot up! and then thread!
5. Always cut your thread near the spool and pull it out from the needle
My German sewing machine mechanic told me off for pulling my thread out from the spool, and there was a waggling finger involved in the telling off!
He explained that there are little feathers holding your thread in place, and by pulling your thread 'backwards' over and over again, you can effectively pull these little feathers out of line, effectively making your sewing machine unrepairable! As well, you strip the thread, leaving bits of thread caught up in the inner workings of the machine.
Since then, I cut my thread at the spool and pull it out in the same direction it always runs! I respect and adore my machines way too much to take the chance!
6. You are Little Bo Peep
What on earth? Have I lost it on this one? Not really :)
I teach children to sew quite often, and I became good at making up little stories they would remember to ensure they always do things the correct way.
So, what's this about Little Bo Peep? Well, when you need to turn your machine's hand wheel, think of it as a little hill with sheep standing on it, and as you are Little Bo Peep, your sheep need to come over the hill towards you, not run away! If you keep this little picture in your mind, you will always turn your hand wheel in the correct direction, and your sheep will always come home (to roost??).
7. Know your machine's 'happy place'
I'm still taking about the hand wheel here. Every time you stop sewing, if your machine doesn't have an automatic needle up/down function, it is up to you to ensure that the machine has done one full revolution and is back to the starting position. To do this, you need to turn the hand wheel to get the needle back to the starting position, with the needle at the highest point, to ensure one complete stitch is created, and the thread is not still under the bobbin.
Failure to do this often results in tangled threads leading to jams and bird's nests under your work.
8. Finished stitching: Needle in 'happy place', presser foot up, pull fabric backwards, trim thread.
Follow this sequence every time! Always in this order, and you'll avoid silly snags. Some machines need a longer thread left than others, to avoid the thread coming out of the needle as you start the next stitch cycle. You will get to know your machine, but a rule of thumb is, use the machine's built in thread trimmer and the thread should always be the correct length.
9. Use good quality thread
Especially as a top thread. Bobbins are less fussy, but cheap thread that sheds bits into your tension discs can cause major problems. As you may know all to well if you have ever had to sit with a long nosed pair of tweezers trying to get a tiny bit of shredded thread out of your machines workings!
Now, I am not saying you need to buy the most expensive, but have a look at the thread before you buy it. It should be even without bumps and lumps, with no dust or discolouration.
Storing your thread in sealable boxes and wrapping a piece of Hugo's amazing tape around each roll keeps those pesky ends tucked in and protects them from dust, prolonging their useful life.
10. Use a guide to sew straight
A simple piece of black electrical tape makes a clear sewing guide to keep the fabric edge up against. It stays in place, can be moved to accommodate any seam allowance requirement, is very visible, and doesn't leave behind sticky residue. A cheap solution that helps you sew straight every time.
Bonus info: The double lift on your presser foot
Every single machine I have ever worked on (and I have tried many) has a double lift option on the presser foot. It has two positions it will stay in - up and down, but then if you give a push on the lever, you will get a bit of extra lift. It will not stay in this position, but return to the up position as soon as you let go of the lever, but is very useful if you need to get a bulky seam under the foot, or a hoop for free motion embroidery.