I've Been Messing Up 了

I just realized that many of my past posts included the particle 了 (because I've gotten into a habit of talking about something I already did) and that the placement of 了 in sentences has been completely wrong. I have been putting 了 after the object in the form of S + V + O + 了. For example, 昨天晚上我喝啤酒了 (attempting to say "Last night I drank beer"). Instead the 了 should be placed right after the verb and the sentence format should be S + V + 了 + O. Let's write a few sample sentences with 了 to hopefully get this right once and for all.

1) 我吃了晚飯。 Wǒ chī le wǎnfàn. I already ate dinner. 

2) 昨天我們看了一電影。 Zuótiān wǒmen kàn le yì diànyǐng. Yesterday we watched a movie. 

3) 他去打球了。 Tā qù dǎ qiú le. He went to play ball. 

4) 他們喝了三啤酒。 Tāmen hē le sān píjiǔ. They drank three beers.