For Verbal Reasoning-
It will depend on your natural reading speed - I've heard of some who would guess the first two sets so that they would have time to properly answer the other 9, but I always found I could read them all in time.
The thing that was catching me out the most were the options with 'can't tell' - I think my biggest advice for those would be to really see if something is actually stated as true/false or if it is left ambiguous (i.e. seemingly not true but not outright said to be false). Like many others say, looking for key words is crucial - most of the time the answer is in one paragraph/section of the text, occasionally it requires several different parts together to form the answer however I found that often took way too long and I would just cut my losses with those questions and guess the most probable answer and move on.
It's really important to not fixate on one question - if you're spending 30 sections looking and still have no idea of the answer just guess, flag and move on, it's really not worth running out of time at the end for that one question.
Don't use your own knowledge - if something's not in the text but you know it to be true or false the answer is 'can't tell' because you can't tell from the text.
Keyboard shortcuts in general like alt + f for flag, alt + n for next alt + p for previous, and clicking the letter A B C or D on the keyboard to select an option. In my test centre the computer mice are awful and don't really click (I knew this from doing driving theory there) so I would avoid the need for the mouse as much as possible.
For Decision Making -
The whiteboard is really your friend. For the syllogisms/logic puzzles these were some of my favourite. Things you need to remember are if it says all X are Y, this does not mean all Y are X. If all X are Y and some Y are Z then some X are Z etc. It might help to replace whatever word/tree/species/country they give you with letters like ABC or XYZ as you have to forget any knowledge you have on the subjects and think like a computer.
For the strongest argument/statement make sure the one you're picking is a specific statement focused on all parts of the question.
For the puzzles like "Anna Bella Cathy and Daniel all buy a piece of fruit. The fruit are red, yellow, blue, purple. None of the fruit are the same colour. Anna does not buy the purple fruit." etc. etc. you have to write them out, like I would write the possibilities for each person under them and eliminate the possibilities by going through the information. For the ones that specify an order/line write the people out in a line as you work through the statements.
Otherwise some of them are maths, like fractions. Others are deducing. With practice and finding strategies that work for you, decision making is something you can really improve on. All the question styles are the same and once you find a working strategy it will keep working every mock.
Hope this helps!