Ms Feather's top tip.
Think of ratio as 'part to part'. For example, when making squash you would want 1 part squash to 4 parts water (depending of course on how strong you like it).
1 part squash to 4 parts water is a ratio of 1:4.
Proportion makes me think of the word portion and I would always say 'Yes please' to a portion of cake or pizza. Ah ha - I can now see a link with fractions...
Proportion is a part, share, or number considered in comparative relation to a whole. If you look at the above example of the squash there is 1 part squash and 4 parts water so how many parts altogether?
There are 5 parts altogether so the proportion of squash would be 1 part out of 5 whole or 1/5.
So in summary, ratio is 'part to part' where as proportion is 'part to whole'.