Puppy at 4months

What should my puppy be achieving/behaving/doing by 4months?
Looking for a bit of a development checklist?
How do I know that I'm on my way to a well behaved grown up?Just want to know how to check I'm doing all the right things etc
Coco is a 4month old JRT/Chihuahua mix...still very small

Coco at 4months by sweetheart-roland, on Flickr

At four months Tucker's nipping was WAY better and he started barking lol. I don't think there is any set "this is what he should have achieved" list. 4 Months is young, I wouldn't expect her to be housebroken yet. As for obedience type stuff, it all depends on how much time you've put into training. Is there anything in particular you're concerned/wondering about?

Not really i just wanted to make sure I was doing the right things,moving onto the next step.etc.Right now I'm really happy with how things are going,she's a fast learner.
-She know's "Sit""Wait""Off""Come here""Lets go!" and also seems to be understanding my bodylanguage/tone of voice more.
-Toilet trained @ home,she goes to her dog toilet 90% of the time.However taking her to other peoples houses is hard and she seems to think carpets=toilet...despite the fact I only use puppy pads when she is in her pen(staying at someone else's house)
-Walking on a leash is o----k...she pulls alot or lags behind....either way she weighs nothing so its not a problem....but it will be when she's older.
-If I can say this I think she is VERY well socialised....I mean she has'nt spent a day inside the house since I've had her,she takes new situations in her stride,loves meeting people happy to play with anyone etc.
Howwwwever the one thing that I can see maybe becoming a problem is the fact my life has NO routine....everyday is different,this works for us now,however its been hard for me to ensure she eats and the same time everyday...which means generally i just leave her dry kibble out.
Is there anything a 4month old puppy SHOULD be doing...or have learnt by now!?
Sorry this is so long,I just feel slightly pressured(by myself)to have a really REALLY well behaved adult dog(what I mean by that is a happy dog and happy owner)

I really do not have a list or anything that I work towards. All pups are different in the way the develop.

I usually look at how far we have come from our starting points Are the things we were working on moving forward for us. Am I happy with the changes I see in the pups behaviors. How is my relationship with the dog evolving....and so on.

Take Watson for example... I am so happy with this boy and the way he is coming along and learning things. I love the way he has bonded to me and my boyfriend. The way he has learned to take direction.

If you feel that she is doing well and that things are heading in a good direction and progressing in the way you are happy with continue just the way you are