As you've already noted, checking your work is vital. Proofreading is a key part of the writing process. It enables you to identify and correct spelling, grammar and punctuation errors. It also gives you the opportunity to improve the content, order and style if you need to.
When proofreading for spelling, the rule must be that if you are unsure of something, check it.
Look it up in a dictionary. You can use an online or book dictionary, or a dictionary app. Online or app dictionaries are not restricted by physical size so tend to have more words.
Use the spell checker on your computer. It can check either as you write or specific words that you type in. Be aware that a spell checker may not pick up all your mistakes, such as incorrect use of homophones.
Use predictive text on your phone messaging app.
Find other texts that are likely to contain the word, and that you know are reliable, and check there.
It can be helpful to keep a personal spelling dictionary for you to log the words you find difficult to spell.
In the text below, highlight all the words that you think might contain spelling errors.