Some of these are very good, others a little bit less so. Granted, they come from a Twitter feed and are therefore spur of the moment, but I'm going to point out a few I disagree with.

Test your hypothesis on simple cases.

I'm not sure this is always true. Ideally we should test in simple cases, but sometimes ruling out strange stuff requires using complicated cases. I'd prefer something like "Test your hypothesis on the simplest cases necessary to make a useful test."

Forming your own opinion is no more necessary than building your own furniture.

I strongly disagree with this. At minimum, one needs to form opinions about which opinions to trust. If you are a good rationalist you can often trust within some confidence the consensus of experts in a field when you have no other data. But not forming opinions easily can let you get taken in by the wrong experts. And not having any opinions will paralyze you.

Thoughts about useless things are not necessarily useless thoughts.

This depends heavily on the definition of "useless".

One of the successes of the Enlightenment is the distinction between beliefs and preferences.

One of the failures of the Enlightenment is the failure to distinguish whether this distinction is a belief or a preference.

I like these two a lot, and I'm going to steal them and use them. I'm not sure the second is completely accurate, certainly most major Enlightenment figures who thought about these issues would argue strongly that this distinction is not a preference.

Not all entities comply with attempts to reason formally about them. For instance, a human who feels insulted may bite you.

This one is very funny and another one I'm stealing. But I'm not sure there's a substantial point here.

Edit and one more:

First eat the low-hanging fruit. Then eat all of the fruit. Then eat the tree.

I'm not sure I agree with this. If I have multiple trees it might be better to get all the low-hanging fruit before I move on to the higher level fruit in any tree. This is especially true because easy results in related fields can help us understand other fields better and help us in our fruit plucking on the nearby trees. Focusing on a single tree until all fruit has been removed is generally not doable in almost any field.