Your write up should go something like this
Aim: What you intend to find out in the experiment (eg, To observe the reaction between HCl and various metals)
Method: How to carry out the experiment (I tend to write instructions, but others write a past tense of what they did. Both are acceptable). If you write precise instructions, such as "Place 6 drops 0.2 mol/L HCl in a 250 mL beaker", you can skip the equipment step.
Results: Use a table, if it's appropriate. And write down everything that you observe (bubbling, smoking, beaker warmed up, produced really bad smell etc), because observations will almost always be worth some marks.
Discussion: This is sometimes optional. But it should include things like ways that the prac could be improved; justifying things that you've done (equipment you've used, why you did things in a certain order), should you feel the need; the validity of the experiment. Risk assessments go here too.
Conclusion: Basically, you say that you've achieved your aim. Sometimes only one setence is necessary (we did one the other day where the conclusion was "We produced esters by combining an alkanol with an alkanoic acid"), but other times, you might need a couple of paragraphs. Depends on how complex your aim was.
Basically, make sure you write down everything, as precisly as possible, and you should be fine. And if you can get a diagram in somewhere, do it. Chem teachers love diagrams