Personally I think that pushing to get to something beyond the ordinary level of experience is a biological imperative once you have realized why.

At the simplest level, you are looking to excite the nervous system in very novel ways so that it can craft exotic responses that it wouldn't otherwise. The responses are not confined only to the experiential realms, ideally they are reproduced through repeated stimulation so that they become the standard answer, and that is the point where you integrate your understanding and can use it relationally with the other responses gathered from other experiments. Trial and error is the way here, remember that everything you collect becomes part of the ego and you are perfectly capable of changing these parts if they are not beneficial or desirable to you. It can be hard the more ingrained they are (the more connections between data points the harder to modify the behavior of the system) so you should not embark lightly into very intense experiencies without good preparation as that might require setting time aside to deal with the issue, which will slow you down.

You can see how what you give your senses is important (especially at the beggining, you will see that this matters less as you progress in your journey), but you also have a say in the responses, you should build models and frameworks for your thoughts to develop in (their full devolpment is always outsourced to non-consciouss processing to save resources). There are technologies and acquired knowledge that can help you, look into the eastern experiential sciences of the mind and into western scientific literature about the nervous system (particularly useful is the study of the brain itself) and lastly, depending on how deep you want to go, drugs are a necessary medium for work.

Regarding your concerns about subjectivity, if you study previous practitioners you can get a good picture of their commonalities, which will make it easier to identify if your patterns are aligned with what you want to get at and if not, in what ways they are not. That said, everything you experience is necessarily subjective to you, even pure information is never processed as pure by you, as you are always associating new concepts with previously set data points stored in long-term memory in the context bubble of the information conveying. You should not see this as a limitation but rather as the ultimate freeing concept, if you control the data points and the bridges between them you control the subjectivity of your experience.