Christian writers and teachers have generally been happy to focus their advice on what Christians do - and to assume that right-thinking will follow right-doing. CS Lewis is a good example of this - he has a tendency to favour action over thought; practical Christian living over the mystical or spiritual tradition.
But, while this works for some people some of the time, this is unsatisfactory for many reasons; the most important of which is that - ultimately - thinking is more important than action. I won't rehearse why, but this blog has argued the point over the past several years, from many angles.
Other problems are that modern Christians, even when they follow Christian rules, generally think in the same materialist leftist way as the mainstream secular world - and over time, the wrong-thinking subverts, erodes and overthrows the 'right' practical aspects - as we have seen in all the major Christian churches. So that the meaning of acts becomes, in many cases, reversed. We get churches who say the same old things, but means by them the opposite - Christian forms with materialist-atheist content.
However, there is a big problem for those (like me) who advocate that Christian living ought to be rooted in Christian thinking - which is the question: How to change thinking?
People know how to change for the better their behaviour, their actions, what they do; but have no idea how they might set-about changing their thinking. The answer to What should I do? is not obvious.
The usual, but unsatisfactory, answer involves some kind of training of thinking, usually by some kind of meditative or prayer practice. But this leads to a kind of 'bootstrap problem' of how to use thinking to change thinking. How can we get a purchase on unwanted thoughts, adopt one sort of thought over another?
Furthermore, it may well be that meditation or prayer is (in practice) just another type of change of behaviour, without change in the mode of thinking. Using words like God and Jesus, but in the same mundane way we would discuss politics, law or holidays.
Also, it generally doesn't work...
By contrast; the way I would advise setting-about changing thinking for the better is to examine you metaphysical assumptions; bring to conscious awareness the basic assumptions you make concerning the nature of reality and all fundamental matters... in particular those that are most important to you.
This is simply a matter of honestly and rigorously questioning yourself why you think something, and following the answers through until you reach something that is a basic assumption, without any further reason for it.
Then examine these basic assumptions.
I have found that this leads to some assumptions that I regarded as wrong, false, or something I did not really believe; and that when these were revised that the whole of thinking - the superficial ideas and thoughts that had previously been supported by these wrong deep-basic assumptions, would begin to change.
So, conscious thinking is used to bring-out unconscious assumptions. And change in false or incoherent deep beliefs is used to reshape and re-order the great mass of surface thoughts.
The stream of thinking is not tackled directly, by trying (usually failing) to use one set of current thoughts against another. Instead, the focus is on bringing-to-conscious-awareness. The trigger for change is that what was unconscious and implicit, becomes conscious and explicit.
It is a matter of redigging the foundations, and then the old building will collapse and a new building will - spontaneously - become constructed upon the new foundations, simply in the course of everyday living and thinking, experiencing and learning.
And because the foundational assumptions are different in form, they are the basis of a different kind of thinking. If the new foundations include deeper depths and wider possibilities, then so will the new daily thoughts deriving from them.
And when we find these everyday thoughts have drifted back into mainstream materialism (as they will...); we can respond by reflecting consciously on our deep assumptions; and from them a new and better kind of thinking will emerge.
Note added: It might very well, and quite reasonably, be argued that if the transformed thinking of Direct Christianity is indeed our task at this time, and if such Direct Christianity necessarily requires the kind of metaphysical reflection I recommend... then there are going to be very few people who will actually do what is really needed. I suspect that this is likely to be correct.