Tried to grow stuff in containers several times now, the only thing I have ever had any success with is hot peppers... a few years ago grew more habaneros and chilis than we could use.  We've attempted several times with a variety of plants since then with limited success, but I recently found some pre-potted plants with cages, advertised for container gardening.  Bought two bell pepper plants and one tomato plant, all about 2' tall with flowers.

Any tips?  I've read most all of the container gardening advise on the internet and that hasn't gotten me very far.  Plants will be in full sun for about 3/4 of the day, partial sun for the rest.  Going to set up an automatic watering system to water every morning.  Will start applying cabaryl early on.  

What else?

I've had very good results growing tomatoes in an Earthbox.

You can find plans on the Internet for making an Earthbox clone, but I used the real thing.

I have very good luck with plastic kitty litter buckets- the taller, squarish ones.  

Drill 5 holes in the bottom; 1/2 or so.  Put a layer or two of big rocks on the bottom.  The dirt is a mixture of organic mulch and Perlite; about 4:1.  I have Rosemary, Thyme, Oregano and los of other herbs that go wild.  I leave them in full sun on the back patio and water them well every couple of days.  'Maters grow well but I like to stick with cherry sizes for a container.  Kale works fine in a shorter bucket.  

Make sure your containers drain well and are kept wet enough.  They will get hot and can dry out easily in hot summer sun.  Support whatever plant early with a good stick- I like the plastic green ones with a Velcro tie, or you can use bamboo with Velcro.  Sounds like maybe you need to work on your soil?  regular "cheap" bagged dirt will work OK, but I'm convinced Perlite and organic fertilizer is the key to container gardens.

my mother does a lot of containers, drying out is her #1 enemy

Leaf lettuce is a perfect match for containers.

I only buy iceburg in the dead of winter.

My scorpion and Ghost pepper did not survive overwintering indoors this year.

Not sure how I killed them....damnit.

My two main problems in the last 2 years trying to bring hot peppers indoors were:

1) Aphids

2) Not enough light

Outdoors, the aphids are kept under good control due to natural predators.  I don't even see aphids when the plants are outdoors, though obviously there are a few there as their population explodes when the plants are brought indoors.