I use Dr Brown's Bottles (££ but worth it) (second baby who has had them) - see below for tip for how to stop them leaking! (you will always hear people say this)
Formula - use Aptamil powder, but will always have a supply of ready made in for those times I haven't got round to making milk (happens frequently!) and for when we're out and about.
Out and About - get a Tommy Tippee flask. A lot of shops/restaurants now eg Costa) will not give you hot water to warm up your milk (good old Health and Safety) so you must take your own. One good exception that will though is good old M&S
. Take a sterilised bottle with you and the ready to go pour stuff.
At home - I pre make up mostly.
Top tip for those with Dr Brown bottles - make up the feed in tommy tippee bottles with lids. Shake them to your hearts content. Pour boiling water in, let stand for 15 mins ish, add the powder then flash cool immediately. Then dump into the fridge.
When you want the milk, take out, whack the tommy tippee bottle in the microwave (shock), quick 40 secs, Done. Pour into a sterilised Dr Browns bottle and you're good to go.
Both of these methods are much much safer than what my friend did (imo) who took out cool boiled water to add to powder and then shook it up to mix whilst she was out. Quite where she got the idea from that so long as the water had been boiled, it would make the feed safe I have no idea.
The reason you use just boiled water is to kill bugs in the powder.
However, what you could do, is take boiling water out with you (in the tommy tippee flask), put cool boiled water into a Dr Brown bottle. Pour say 3 oz of hot water into a tommy tippee shaker, add 3 scoops of powder, shake and then add the remaining 3 oz of cool water to mix. Then put all back into the Dr Browns bottle. This is another good way to make a safe feed whilst you are out.