What follows is personal and based on my experiences with learning Polish (so far), a language which I've found difficult.
So, what I've written is based on what I have learnt up to this point, and what I would have found useful to know when I was first beginning.
The first thing to be aware of is that Polish is difficult. It is much more difficult initially than say Spanish or Italian.
I'm not writing this to discourage anyone, but so that it is much better to know what you are attempting and so not to become discouraged if your progress is slow.
Forewarned is forearmed.
The FSI has categorised languages into five levels of difficuly (for English speakers) with the first category containing the easiest languages to learn and the fifth the most difficult.
Initially, I was unsure how to start as the language is so, ahem, foreign. At first glance, all you can see is a ridiculous number of consonants, diacritics and few vowels. It is difficult to see the wood from the trees.
So, if I was starting again (and if I ever learn any Russian or other slavic language), I would :
I would have spend more time becoming comfortable with the pronunciation before anything else.
I don't mean being obsesional or attempting to pronounce words perfectly, but if for example you see the word ciemniejsze, does it trip off your tongue?
Being happy with the pronunciation makes the words easier to memorize.
I would learnt more very basic phrases by heart at the beginning. How are you? My name is ...?
There is a lot of debate on when you should start speaking. Some people start speaking immediately, and others after some time.
Personally, I don't see it as a big deal, but a matter of personal preference, unless you have an urgent need to communicate, for example, if you live in the country where the language is spoken.
Obviously, to get good at speaking, you have to speak a lot.
I have no urgent need to communicate (as I don't live in Poland), but learning more basic Polish phrases initially would have boosted my confidence that I could learn Polish - especially at the start.
And also really, I've never been interested in saying 'My name is ...', 'where do you live?', which is all you can do at a beginner level. I'm more interested in talking about politics/society and so on. So while I've used iTalki to have a few lessons and can say 'My name is ...', 'How are you ...', and various other pleasantries I haven't really bothered with Polish.'
Conversely, with Italian, I started chatting almost immediately, because I could (if someone spoke slowly) more or less understand. Even if you know a few Polish phrases, you won't understand any responese.
I would learn the Polish sentences on Surface languages. There are lots of them, and they include a lot of basic Polish vocabulary and langueg structures.
Getting back to starting to learn Polish, these sentences are incredibly useful not only for the vocabulary contained but because they contain many useful phrases.
For example, the sentence Kupiłem go dwa tygodnie temu 'I bought in two weeks ago' contains the phrase dwa tygodnie temu 'two weeks ago', which it the sort of phrase that occurs frequently in normal conversation. This is mega useful in Polish, expecially at the start, because as it has a complicated grammar it is difficult to put sentences together correctly. Phrases help you do this.
So, at this point, you have learnt some basic Polish phrases and the 500 sentences.
But you also need to learn how to roughly put sentences together yourself. And this means bit by bit grappling with Polish grammar.
In the sentence, Moi przyjaciele przeprowadzili się do Australii sześć lat temu 'My friends moved to Australia six years ago', there is a plural. Moi przyjaciele 'my friends' '
And you can start to pick out patterns.
Comprehension takes a lot of time. Understanding well is the elephant in the room in general with language learning.
There are different levels of conversation, face to face, with a teacher, the radio, films and so on.
It takes time with any language, and I'm finding the process slower than I expected with Polish, and I would definitely have started listening to comprehensible audio earlier.
I bought the daily Polish stories from Mr Real Polish, as there is a definite lack of accessible audio for free (apart from here of course).
Speaking. It appears that I don't put much emphasis on speaking, which isn't actually the case. It is more that I have limited amounts of time.
I have Spanish and Italian language exchanges and this has massively helped me with these languages. The more you speak, the better you get at speaking. One day I'll focus on this with Polish.
At the moment my Polish journey is in abeyance. I don't know if or when I will resume the path.
The language isn't impossible. It is certainly difficult but not impossible. My reasons for stopping were not due to slow progress but more a lack of needing to use the language. I lacked the need or impetus to move to the next level.
Maybe one day ...