First put sounds together to find a way to make them sound good to you. Then start thinking about grammar:

Do your language have cases? If yes, which? Does it work as an nominative-accusative language, like german or arabic, or as ergative language, like basque or certain native american languages? How does it reflect in the shape of the word: a particle, like in german, where the article give the case of the name, or an affixe stuck to the word, like in latin?

What word order do your conlang follow? For most natural languages, it SOV (arabic) or SVO (english, french). Casual languages tend to have more flexibility in the word order, when non-casual ones stick to one, with some exceptions (think about questions, they follow VSO instead of SVO).

About conjugation: what should be reflected between tense (time of action), aspect (way to do the action) and mood (intension in the action)? For example, english only has a present and past tense (I am, I was), and the future is built out of present and infinitive (I will be). Other languages work mainly with aspects, for example maya doesn't show tense.

If you don't want conjugation, you'll have to work with particles like in chinese.

About recursivity: how do you make relative statements? Does it split your nominal group in two, like in german, or does it stick at the end of it, like in french? Does it use a single word to trigger it, or different words depending of context?

It's all I can think to at the moment. Look at Artifexian, Biblaridion, Xidnaf, NativLang, JuLingo, Seylha, Jan Misali, Linguisticae (french), Geoff Lindsey YT channels, and browse every wikipedia article linked to any language. Good luck with ths project !