Materials
- Cement
- Fine aggregate (sharp sand)
- Coarse aggregate (10mm gravel)
- Water

Mix ratios are always given in the format cement : fine aggregate : coarse aggregate

Example: 1:2:3 - this means 1 part cement, 2 parts sharp sand, 3 parts gravel - water is also added to the achieve the desired consitencey and strength. For info on water addition click here

Lean concrete - provides uniform surface to the foundation concrete and prevents the direct contact of foundation concrete from the soil.
M5 1:5:10
M7.5 1:4:8
Ordinary concrete - can be used in construction of levelling course, bedding for footing, concrete roads
M10 1:3:6 
M15 1:2:4
M20 1:1.5:3
Standard concrete - used in construction of slabs, beams, columns, footings, etc.
M25 1:1:2
M30 1:0.75:1.5
M35 1:0.5:1
M40 1:0.25:0.5

Cement and sharp sand mixes can also be used - 1:3 & 1:4 (cement:sharp sand). These mixes wont be as strong but are easier to get a smooth finish with. Sharp sand is also about 20% cheaper than gravel per bag.

Reinforcement
Use rebar or wire mesh where possible.

Vibration
If you are making anything in a form/mold vibrate it as mush as possible, this will knock out any air gaps and help the concrete fully fill the form so it doesn’t come out looking like swiss cheese.

Time
Before you skate anything, leave it a bare minimum of 1 week, ideally 2 weeks +