Alex
Hello and welcome,
the fist thing you need to do is chill, it may sound condasenting (excuse spelling), but to do you best times you need to relax! That is the most important thing. The next is to enjoy it, becuase if you don't you woun't do the next thing! Practice, it doesn't make too much difference at the beginning what method you use, an ounce of practice is better than tonnes of theory!!!
Though two tips, firstly you will find that you will do you best time on about your fourth or fifth hold of the seasion. Secondly, breath in a relaxed manor between holds for a few minutes. You would have found these out youself, but it my have taken some time, it took me a few years to work that out.
As you practice more you intuatively develop your own style, which is more important than trying to mimic someone elses, as their's may not suit you.
With regards to packing, myself I don't do it, beacuse at the moment I don't see the need for it just yet! As I haven't found my limit. When I get to the limit then I may use packing to overcome it.
So to recap the main points:
1) Relax
2) Enjoy it
3) Practice
4) Develop an understanding of you and your body
This is from my own experience and just a little anecdote, I achieved my best dry static time about a year before I discovered freediving and after nearly two years of freediving I have come close, but haven't betten it! Mainly because I enjoy other things to do with freediving, I don't enjoy static so I don't practice it enough.
to answer your question on how long you will be able to hold you breath for:
It depends on how far you take it, you can always get better with practice.
Play with it and have fun
Sam
best dry static time: 6min39sec