How do I know if I have tartar on my teeth besides going to dentist?

Whitish or yellow. Tartar is hardened plaque stuck to the teeth. Sometimes you can see it as a whitish or yellowish "ring" along the gumline. If you can't remove it easily with brushing, it is likely tartar. See a dentist to have it removed.
Look on the back. On the back of lower front teeth is the most common spot to see it. It is not easy to see without a small mirror and a second to see into the small one. Look along gum lines. If you see a yellowish white crusty material that has ledges and very red gums around it, or the shape is weird, likely you have calculus aka tartar. Go to your dentist.
Signs & Symptoms. The most common sign of tartar is a yellow or brown color to teeth or gums. The only way for sure to detect tartar under your gums and to remove it is to see your dentist for examination.
Look for deposits. Look for deposits along gum line, especially along backs of bottom front teeth, of white to yellow to tan crusty material. You can't get it off, you need a dentist for that. You can't see the tarter that develops under the gum line, especially in the back. You can't see the soft plaque that is the tarter precursor. You can't avoid regular dental check-ups/cleanings. You have to go regularly.