The exercise qulity when you're tired will suffer and so will progress.
(Leg raises, Pikes, Knee tucks are some example exercises)
STEP 2 - Train the obliques second (muscles to the side of the stomach)
They're not classed as an abdominal muscles BUT....
They can tilt the hips posteriorly similar to the lower abs.
(basically tilt the front of the hips upwards)
This means they can be kind of classed as a lower abdominal.
STEP 3 - Finish with the upper Ab's
Typically these are people's over-dominant abdominal muscles so DON'T prioritise them.
(They're sat in a tightened/shortened position everyday when we sit at desks leaning forwards, sit in the car or slouch on the sofa)
Leave these until the end and keep the work on these minimal!
STEP 4 - Prioritise lower rep ranges (8-12 reps).
The Ab's are fast twitch fibred and are Phasic muscles
Basiacllty meaning they're intended for power and strength work, not long duration work.
If you want them to respond well, stick with training them that way.
They'll respond much better to lower rep ranges as opposed to higher rep ranges such as 15-20+ reps.
BIG BIG PIECE Of ADVICE....
Remember that the entire core is ALWAYS involved through major exercises...
The overhead press, Deadlifts, Squats and Lunges being prime examples.
The key to feeling them during these exercises simply comes down to refining technique.
Enjoy and try sticking with these basic rules.
If you want to address these aspects in more details,
Refine nutrition and other key aspects..
I've put together a link just for you.
LINK - https://grahamlawson.wufoo.eu/forms/coaching-session-request/
Take Care,
Graham Lawson - Weight Loss & Performance Coach