It's the Russian language! There are no strong rules by the verb conjugation. It's like Spanish, Italian or French verbs, you have to memorize the special conjugations of many verbs: ждать - я жду, ты ждёшь; мять - я мну, ты мнёшь; летать - я лечу, ты летишь; пахать - я пашу, ты пашешь, мочь - я могу, ты можешь, они могут; видеть - я вижу, ты видишь, любить - я люблю, ты любишь etc.

The truth is that in the beginning you need to learn Russian language and then you will try to understand rules. In Russia only who're reading a lot of classical Russian books he knows Russian and can write correctly. Who learns rules he doesn't know the language.))))

There is not real way. That's why it makes much sense to first learn TWO stems of a verb: one for forming present tense conjugation, and the other for past and infinitive. These two stems are not random of course. If you desire to tremble in fear, more than 15 classes of verbs are found in Russian, depending on how exactly one stem corresponds to the other. If you don't want to tremble in fear, only a few of these are productive. "Ждать" belongs to a compact non-productive class of АТЬ/ЯТЬ-verbs (meaning, it'll take you time to learn the verbs but newly created verbs do not go there anymore). Other verbs of the same class: брать, писать, сказать, молчать, лежать, смеяться, понять, звать, начать, дышать. They have the following forms in 1st person singular: беру, пишу, скажу, молчу, лежу, смеюсь, пойму, зову, начну, дышу. If you ignore the consonant mutations in some of them, you can see that these verbs on ать/ять exhibit the same pattern: they don't have a vowel at the end of a present-tense stem.